Export default text parser plugins

This makes it easier for apps to app-specific build subclasses of
these plugins.

Closes #2428

Change-Id: I4fde7de76c139bfeddc1afecccf9374a49ecee19

Author: joeyparrish

lib/text/mp4_ttml_parser.js

@@ -13,6 +13,7 @@ goog.require('shaka.util.Mp4Parser');
 
 /**
  * @implements {shaka.extern.TextParser}
+ * @export
  */
 shaka.text.Mp4TtmlParser = class {
   constructor() {
@@ -23,7 +24,10 @@ shaka.text.Mp4TtmlParser = class {
     this.parser_ = new shaka.text.TtmlTextParser();
   }
 
-  /** @override **/
+  /**
+   * @override
+   * @export
+   */
   parseInit(data) {
     const Mp4Parser = shaka.util.Mp4Parser;
 
@@ -49,7 +53,10 @@ shaka.text.Mp4TtmlParser = class {
     }
   }
 
-  /** @override **/
+  /**
+   * @override
+   * @export
+   */
   parseMedia(data, time) {
     const Mp4Parser = shaka.util.Mp4Parser;
 

lib/text/mp4_vtt_parser.js

@@ -21,6 +21,7 @@ goog.require('shaka.util.TextParser');
 
 /**
  * @implements {shaka.extern.TextParser}
+ * @export
  */
 shaka.text.Mp4VttParser = class {
   constructor() {
@@ -33,7 +34,10 @@ shaka.text.Mp4VttParser = class {
     this.timescale_ = null;
   }
 
-  /** @override */
+  /**
+   * @override
+   * @export
+   */
   parseInit(data) {
     const Mp4Parser = shaka.util.Mp4Parser;
 
@@ -86,7 +90,10 @@ shaka.text.Mp4VttParser = class {
     }
   }
 
-  /** @override */
+  /**
+   * @override
+   * @export
+   */
   parseMedia(data, time) {
     if (!this.timescale_) {
       // Missing timescale for VTT content. We should have seen the init

lib/text/ttml_text_parser.js

@@ -18,14 +18,21 @@ goog.require('shaka.util.XmlUtils');
 
 /**
  * @implements {shaka.extern.TextParser}
+ * @export
  */
 shaka.text.TtmlTextParser = class {
-  /** @override */
+  /**
+   * @override
+   * @export
+   */
   parseInit(data) {
     goog.asserts.assert(false, 'TTML does not have init segments');
   }
 
-  /** @override */
+  /**
+   * @override
+   * @export
+   */
   parseMedia(data, time) {
     const TtmlTextParser = shaka.text.TtmlTextParser;
     const XmlUtils = shaka.util.XmlUtils;

lib/text/vtt_text_parser.js

@@ -17,15 +17,20 @@ goog.require('shaka.util.TextParser');
 
 /**
  * @implements {shaka.extern.TextParser}
+ * @export
  */
 shaka.text.VttTextParser = class {
-  /** @override */
+  /**
+   * @override
+   * @export
+   */
   parseInit(data) {
     goog.asserts.assert(false, 'VTT does not have init segments');
   }
 
   /**
    * @override
+   * @export
    */
   parseMedia(data, time) {
     const VttTextParser = shaka.text.VttTextParser;