Fall back to fast forward by seeking on large rate values.

If a value given to player.trickPlay() is outside of what
the browsers accepts for video.playbackRate, fall back
to fast forward by seeking, same as we do for rewind.

Closes #1957.

Change-Id: I12275377b70dc1d0e2ece7f5647e6590f0304cf5

Author: ismena

lib/media/play_rate_controller.js

@@ -113,11 +113,22 @@ shaka.media.PlayRateController = class {
     const rate = this.calculateCurrentRate_();
 
     if (rate >= 0) {
-      this.applyRate_(rate);
-      return;
+      try {
+        this.applyRate_(rate);
+        return;
+      } catch (e) {
+        // Fall through to the next clause.
+        //
+        // Fast forward is accomplished through setting video.playbackRate.
+        // If the play rate value is not supported by the browser (too big),
+        // the browsers will throw.
+        // Use this as a cue to fall back to fast forward through repeated
+        // seeking, which is what we do for rewind as well.
+      }
     }
 
-    // When moving backwards, set the playback rate to 0 so that we can manually
+    // When moving backwards or forwards in large steps,
+    // set the playback rate to 0 so that we can manually
     // seek backwards with out fighting the playhead.
     this.timer_.tickEvery(this.pollRate_);
     this.applyRate_(0);