Fixing some typos and removing references to "checked mode" (cfug#1191)

* Fixing some typos and removing references to "checked mode", which doesn't exist in Dart 2.

* Incorporating feedback.

Author: sfshaza2

.firebaserc

@@ -3,6 +3,8 @@
     "default": "sweltering-fire-2088",
     "flutter-io": "sweltering-fire-2088",
     "staging-1": "flutter-io-staging-1",
-    "pc2": "ng2-io"
+    "pc2": "ng2-io",
+    "sz" :  "sz-flutter",
+    "sz2" : "sz-flutter-2"
   }
 }

src/debugging.md

@@ -19,8 +19,9 @@ check out [Flutter Performance Profiling](/ui-performance/).
 ## The Dart Analyzer
 
 Before running your applications, test your code with `flutter analyze`. This
-tool (which is a wrapper around the `dartanalyzer` tool) will analyze your code
-and help you find possible mistakes. If you're using a [Flutter enabled IDE/editor](/get-started/editor/),
+tool (which is a wrapper around the `dartanalyzer` tool) analyzes your code
+and helps you find possible mistakes. If you're using a
+[Flutter enabled IDE/editor](/get-started/editor/),
 this is already happening for you.
 
 The Dart analyzer makes heavy use of type annotations that you put in
@@ -44,8 +45,8 @@ information on Observatory, see
 
 If you use Observatory for profiling, make sure to run your
 application in profile mode, by passing `--profile` to the `flutter
-run` command. Otherwise, the main thing that will appear on your
-profile will be the debug asserts verifying the framework's various
+run` command. Otherwise, the main thing that appears on your
+profile is the debug asserts verifying the framework's various
 invariants (see "Debug mode assertions" below).
 
 ### `debugger()` statement
@@ -69,7 +70,7 @@ void someFunction(double offset) {
 
 ## `print` and `debugPrint` with `flutter logs`
 
-The Dart `print()` function will output to the system console, which
+The Dart `print()` function outputs to the system console, which
 you can view using `flutter logs` (which is basically a wrapper around
 `adb logcat`).
 
@@ -92,13 +93,17 @@ of the object.
 ## Debug mode assertions
 
 During development, you are highly encouraged to use Flutter's "debug"
-mode, sometimes referred to as "checked" mode. This is the default if
-you use `flutter run`. In this mode, the Dart `assert` statement is
-enabled, and the Flutter framework uses this to perform many runtime
-checks verifying that invariants are not being violated.
-
-When an invariant is violated, it is reported to the console, with
-some context information to help with tracking down the source of the
+mode. This is the default if you use `flutter run` or the bug icon
+in Android Studio. Some tools support assert statements through the
+command-line flag `--enable-asserts`.
+In this mode, Dart assert statements are enabled, and the Flutter
+framework evaluates the argument to each assert statement encountered during
+execution, throwing an exception if the result is false. This allows
+developers to enable or disable invariant checking, such that the associated
+performance cost is only paid during debugging sessions.
+
+When an invariant is violated, it's reported to the console, with
+some context information to help track down the source of the
 problem.
 
 To turn off debug mode, and use release mode, run your application
@@ -107,6 +112,9 @@ debugger. An in-between mode that turns off all the debugging aids
 _except_ the Observatory, known as "profile mode", is available also,
 using `--profile` instead of `--release`.
 
+For more information, see
+[Flutter's modes](https://github.com/flutter/flutter/wiki/Flutter's-modes).
+
 ## Debugging application layers
 
 Each layer of the Flutter framework provides a function to dump its
@@ -151,7 +159,7 @@ class AppHome extends StatelessWidget {
 }
 ```
 
-...will output something like this (the precise details will vary on
+...outputs something like this (the precise details vary by
 the version of the framework, the size of the device, and so forth):
 
 ```
@@ -246,8 +254,8 @@ from being pressed to being released, it coincides with the
 [`FlatButton`](https://docs.flutter.io/flutter/material/FlatButton-class.html)
 object calling
 [`setState()`](https://docs.flutter.io/flutter/widgets/State/setState.html)
-and thus marking itself dirty. That is why if you look at the dump you
-will see that specific object marked "dirty". You can also see what
+and thus marking itself dirty. That is why, when you look at the dump you
+should see that specific object marked as "dirty". You can also see what
 gesture listeners have been registered; in this case, a single
 GestureDetector is listed, and it is listening only to a "tap" gesture
 ("tap" is the output of a `TapGestureDetector`'s `toStringShort`
@@ -754,19 +762,19 @@ flag, which causes layers to be overlayed with a rotating set of
 colors whenever they are repainted.
 
 All of these flags only work in debug mode. In general, anything in
-the Flutter framework that starts with "`debug...`" will only work in
+the Flutter framework that starts with "`debug...`" only works in
 debug mode.
 
 ## Debugging animations
 
-The easiest way to debug animations is to slow them way down. To do
-that, set the
+The easiest way to debug animations is to slow them down. To do that,
+set the
 [`timeDilation`](https://docs.flutter.io/flutter/scheduler/timeDilation.html)
 variable (from the `scheduler` library) to a number greater than 1.0,
 for instance, 50.0. It's best to only set this once on app startup. If
 you change it on the fly, especially if you reduce it while animations
 are running, it's possible that the framework will observe time going
-backwards, which will probably result in asserts and generally will
+backwards, which will probably result in asserts and generally
 interfere with your efforts.
 
 ## Debugging performance problems
@@ -776,7 +784,7 @@ set the
 [`debugPrintMarkNeedsLayoutStacks`](https://docs.flutter.io/flutter/rendering/debugPrintMarkNeedsLayoutStacks.html)
 and
 [`debugPrintMarkNeedsPaintStacks`](https://docs.flutter.io/flutter/rendering/debugPrintMarkNeedsPaintStacks.html)
-flags respectively. These will log a stack trace to the console any
+flags, respectively. These log a stack trace to the console any
 time a render box is asked to relayout and repaint. You can use the
 `debugPrintStack()` method from the `services` library to print your
 own stack traces on demand, if this kind of approach is useful to you.
@@ -828,7 +836,7 @@ Timeline.finishSync();
 Then open your app's Observatory's timeline page, check the 'Dart'
 recording option and perform the function you want to measure.
 
-Refreshing the page will display the chronological timeline records
+Refreshing the page displays the chronological timeline records
 of your app in Chrome's [tracing tool](https://www.chromium.org/developers/how-tos/trace-event-profiling-tool).
 
 Be sure to `flutter run` your app with the `--profile` flag to ensure
@@ -848,18 +856,18 @@ application in a stack and putting a widget on your stack that was
 created by calling
 [`PerformanceOverlay.allEnabled()`](https://docs.flutter.io/flutter/widgets/PerformanceOverlay/PerformanceOverlay.allEnabled.html).)
 
-This will show two graphs. The top one is the time spent by the GPU
+This shows two graphs. The top one is the time spent by the GPU
 thread, the bottom one is the time spent by the CPU thread. The white
 lines across the graphs show 16ms increments along the vertical axis;
 if the graph ever goes over one of these lines then you are running at
 less than 60Hz. The horizontal axis represents frames. The graph is
 only updated when your application paints, so if it is idle the graph
-will stop moving.
+stops moving.
 
 This should always be done in release mode, since in debug mode
 performance is intentionally sacrificed in exchange for expensive
 asserts that are intended to aid development, and thus the results
-will be misleading.
+are misleading.
 
 ## Material grid
 
@@ -871,7 +879,7 @@ over the application to help verify alignments. To that end, the
 [`MaterialApp`
 constructor](https://docs.flutter.io/flutter/material/MaterialApp/MaterialApp.html)
 has a `debugShowMaterialGrid` argument which, when set to `true` in debug
-mode, will overlay such a grid.
+mode, overlays such a grid.
 
 You can also overlay such a grid on non-Material applications by using
 the

src/flutter-for-ios.md

@@ -1934,13 +1934,13 @@ class _SampleAppPageState extends State<SampleAppPage> {
     return _errorText;
   }
 
-  bool isEmail(String em) {
+  bool isEmail(String emailString) {
     String emailRegexp =
         r'^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$';
 
-    RegExp regExp = RegExp(p);
+    RegExp regExp = RegExp(emailRegexp);
 
-    return regExp.hasMatch(em);
+    return regExp.hasMatch(emailString);
   }
 }
 {% endprettify %}

src/flutter-for-react-native/index.md

@@ -9,7 +9,7 @@ This document is for React Native (RN) developers looking to apply their existin
 This document can be used as a cookbook by jumping around and finding questions that are most relevant to your needs.
 
 
-*****  
+*****
 
 * TOC Placeholder
 {:toc}
@@ -232,11 +232,11 @@ _getIPAddress() {
 
 Try it out in [DartPad](https://dartpad.dartlang.org/b68eb981456c5eec03daa3c05ee59486).
 
-For more information, see the documentation on [Futures](https://www.dartlang.org/tutorials/language/futures).  
+For more information, see the documentation on [Futures](https://www.dartlang.org/tutorials/language/futures).
 
 #### `async` and `await`
 
-The `async` function declaration defines an asynchronous function.  
+The `async` function declaration defines an asynchronous function.
 
 In JavaScript, the `async` function returns a `Promise`. The `await` operator is
 used to wait for a `Promise`.
@@ -389,18 +389,18 @@ void main() {
 
 
 
-The following images show the Android and iOS UI for the basic Flutter "Hello world!" app.  
+The following images show the Android and iOS UI for the basic Flutter "Hello world!" app.
 
 |Android |iOS |
 |:---:|:--:|
-|<img src="images/hello_world_basic_android.png?raw=true" style="width:300px;" alt="Loading">|<img src="images/hello_world_basic_iOS.png?raw=true" style="width:300px;" alt="Loading">|  
+|<img src="images/hello_world_basic_android.png?raw=true" style="width:300px;" alt="Loading">|<img src="images/hello_world_basic_iOS.png?raw=true" style="width:300px;" alt="Loading">|
 
 <br>
 Now that you've seen the most basic Flutter app, the next section shows
  how to take advantage of Flutter's rich widget libraries to create a modern,
   polished app.
 
-### How do I use widgets and nest them to form a widget tree?  
+### How do I use widgets and nest them to form a widget tree?
 
 In Flutter, almost everything is a widget.
 
@@ -412,9 +412,9 @@ the root widget serves this role.
 
 A widget can define:
 
-* A structural element—like a button or menu  
-* A stylistic element—like a font or color scheme  
-* An aspect of layout—like padding or alignment  
+* A structural element—like a button or menu
+* A stylistic element—like a font or color scheme
+* An aspect of layout—like padding or alignment
 
 The following example shows the "Hello world!" app using widgets from the
  Material library. In this example, the widget tree is nested inside the
@@ -452,7 +452,7 @@ The following images show "Hello world!" built from Material Design widgets. You
 
 |Android |iOS |
 |:---:|:--:|
-|<img src="images/6b18b6e158b15685.png?raw=true" style="width:275px;" alt="Loading">|<img src="images/2e973d40d6e82114.png?raw=true" style="width:300px;" alt="Loading">|  
+|<img src="images/6b18b6e158b15685.png?raw=true" style="width:275px;" alt="Loading">|<img src="images/2e973d40d6e82114.png?raw=true" style="width:300px;" alt="Loading">|
 
 <br>
 
@@ -469,7 +469,7 @@ The important difference between stateless and stateful widgets is that
 In simple or basic apps it's easy to nest widgets, but as the code base gets
 larger and the app becomes complex, you should break deeply nested widgets into
 functions that return the widget or smaller classes. Creating separate functions
-and widgets allows you to reuse the components within the app.  
+and widgets allows you to reuse the components within the app.
 
 ### How do I create reusable components?
 
@@ -573,7 +573,7 @@ void main(){
 In Flutter, the entry point file is `’projectname’/lib/main.dart` and execution
 starts from the `main` function.
 
-### How are files structured in a Flutter app?  
+### How are files structured in a Flutter app?
 
 When you create a new Flutter project, it builds the following directory structure. You can customize it later, but this is where you start.
 <pre>
@@ -600,8 +600,8 @@ When you create a new Flutter project, it builds the following directory structu
 A Flutter resource or asset is a file that is bundled and deployed with your app
 and is accessible at runtime. Flutter apps can include the following asset
 types:
-* Static data such as JSON files  
-* Configuration files  
+* Static data such as JSON files
+* Configuration files
 * Icons and images (JPEG, PNG, GIF, Animated GIF, WebP, Animated WebP, BMP,
   and WBMP)
 
@@ -675,7 +675,7 @@ In Flutter, install a package using the following instructions:
 
 1. Add the package name and version to the `pubspec.yaml` dependencies section.
 The example below shows how to add the `google_sign_in` Dart package to the
-`pubspec.yaml` file. Check your spaces when working in the YAML file because **white space matters**!  
+`pubspec.yaml` file. Check your spaces when working in the YAML file because **white space matters**!
 <!-- skip -->
 ```yaml
 dependencies:
@@ -1132,7 +1132,7 @@ internal state to manage.
  describing does not depend on anything other than the configuration information
  in the object itself and the [`BuildContext`](https://docs.flutter.io/flutter/widgets/BuildContext-class.html) in which the widget is inflated.
 
-[AboutDialog](https://docs.flutter.io/flutter/material/AboutDialog-class.html),  [CircleAvator](https://docs.flutter.io/flutter/material/CircleAvatar-class.html), and [Text](https://docs.flutter.io/flutter/widgets/Text-class.html) are examples of stateless widgets which subclass  [StatelessWidget](https://docs.flutter.io/flutter/widgets/StatelessWidget-class.html).
+[AboutDialog](https://docs.flutter.io/flutter/material/AboutDialog-class.html),  [CircleAvatar](https://docs.flutter.io/flutter/material/CircleAvatar-class.html), and [Text](https://docs.flutter.io/flutter/widgets/Text-class.html) are examples of stateless widgets which subclass  [StatelessWidget](https://docs.flutter.io/flutter/widgets/StatelessWidget-class.html).
 
 
 <!-- skip -->
@@ -1601,9 +1601,9 @@ const MyApp = TabNavigator(
 ```
 
 Flutter provides several specialized widgets for drawer and tab navigation:
-* [TabController](https://docs.flutter.io/flutter/material/TabController-class.html)—Coordinates the tab selection between a TabBar and a TabBarView.  
-* [TabBar](https://docs.flutter.io/flutter/material/TabBar-class.html) —Displays a horizontal row of tabs.  
-* [Tab](https://docs.flutter.io/flutter/material/Tab-class.html)—Creates a material design TabBar tab.  
+* [TabController](https://docs.flutter.io/flutter/material/TabController-class.html)—Coordinates the tab selection between a TabBar and a TabBarView.
+* [TabBar](https://docs.flutter.io/flutter/material/TabBar-class.html) —Displays a horizontal row of tabs.
+* [Tab](https://docs.flutter.io/flutter/material/Tab-class.html)—Creates a material design TabBar tab.
 * [TabBarView](https://docs.flutter.io/flutter/material/TabBarView-class.html)—Displays the widget that corresponds to the currently selected tab.
 
 
@@ -2159,7 +2159,7 @@ app.
 In React Native, Animated APIs are used to create animations.
 
 In Flutter, use the [`Animation`](https://docs.flutter.io/flutter/animation/Animation-class.html)
-class and the [`AnimationController`](https://docs.flutter.io/flutter/animation/AnimationController-class.html) class.  
+class and the [`AnimationController`](https://docs.flutter.io/flutter/animation/AnimationController-class.html) class.
 `Animation` is an abstract class that understands its current value and
 its state (completed or dismissed). The `AnimationController` class lets you
 play an animation forward or in reverse, or stop animation and set the animation
@@ -2305,13 +2305,14 @@ child: Dismissible(
 
 |Android|iOS|
 |:---:|:--:|
-|<img src="images/card_swipe_android.gif?raw=true" style="width:300px;" alt="Loading">|<img src="images/card_swipe_iOS.gif?raw=true" style="width:300px;" alt="Loading">|  
+|<img src="images/card_swipe_android.gif?raw=true" style="width:300px;" alt="Loading">|<img src="images/card_swipe_iOS.gif?raw=true" style="width:300px;" alt="Loading">|
 
 <br>
 
 ## React Native and Flutter Widget equivalent components
 
-The following table lists commonly-used React Native components mapped to the corresponding Flutter widget and common widget properties.
+The following table lists commonly-used React Native components mapped to the
+corresponding Flutter widget and common widget properties.
 
 | React Native Component                                                                    | Flutter Widget                                                                                             | Description                                                                                                                            |
 | ----------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |

src/get-started/codelab/index.md

@@ -326,7 +326,7 @@ a child inside the existing `MyApp` stateless widget.
     build method that generates the word pairs by moving the
     word generation code from `MyApp` to `RandomWordsState`.
 
- 3. Add the `build()` method to `RandomWordState`:
+ 3. Add the `build()` method to `RandomWordsState`:
 
     <!-- skip -->
     {% prettify dart %}