[Android WebView] Propagate media keys to the AudioManager when WebVi…

…ew is active.

Propagate media keys to the android AudioManager when a Webview
is active. This is to fix the problem of the start/stop/next etc.
media keys not working on a bluetooth headset when a WebView is
in focus, in particular when ads are shown.

[email protected]
BUG=479786
NOTRY=true
NOPRESUBMIT=true

Review URL: https://codereview.chromium.org/1099903005

Cr-Commit-Position: refs/heads/master@{#326591}
(cherry picked from commit 741d61b)

Review URL: https://codereview.chromium.org/1099343003

Cr-Commit-Position: refs/branch-heads/2357@{#222}
Cr-Branched-From: 59d4494-refs/heads/master@{#323860}

android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java

@@ -7,6 +7,7 @@
 import android.annotation.SuppressLint;
 import android.content.ContentResolver;
 import android.content.Context;
+import android.media.AudioManager;
 import android.net.Uri;
 import android.os.AsyncTask;
 import android.os.Handler;
@@ -78,9 +79,38 @@ public void handleKeyboardEvent(KeyEvent event) {
             }
             if (direction != 0 && tryToMoveFocus(direction)) return;
         }
+        handleMediaKey(event);
         mContentsClient.onUnhandledKeyEvent(event);
     }
 
+    /**
+     * Redispatches unhandled media keys. This allows bluetooth headphones with play/pause or
+     * other buttons to function correctly.
+     */
+    private void handleMediaKey(KeyEvent e) {
+        switch (e.getKeyCode()) {
+            case KeyEvent.KEYCODE_MUTE:
+            case KeyEvent.KEYCODE_HEADSETHOOK:
+            case KeyEvent.KEYCODE_MEDIA_PLAY:
+            case KeyEvent.KEYCODE_MEDIA_PAUSE:
+            case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
+            case KeyEvent.KEYCODE_MEDIA_STOP:
+            case KeyEvent.KEYCODE_MEDIA_NEXT:
+            case KeyEvent.KEYCODE_MEDIA_PREVIOUS:
+            case KeyEvent.KEYCODE_MEDIA_REWIND:
+            case KeyEvent.KEYCODE_MEDIA_RECORD:
+            case KeyEvent.KEYCODE_MEDIA_FAST_FORWARD:
+            case KeyEvent.KEYCODE_MEDIA_CLOSE:
+            case KeyEvent.KEYCODE_MEDIA_EJECT:
+            case KeyEvent.KEYCODE_MEDIA_AUDIO_TRACK:
+                AudioManager am = (AudioManager) mContext.getSystemService(Context.AUDIO_SERVICE);
+                am.dispatchMediaKeyEvent(e);
+                break;
+            default:
+                break;
+        }
+    }
+
     @SuppressLint("NewApi")  // View#getLayoutDirection requires API level 17.
     @Override
     public boolean takeFocus(boolean reverse) {