Add support for tab migration to DialogSurface

media/base/android/java/src/org/chromium/media/IDialogSurfaceHolder.aidl

Index: media/base/android/java/src/org/chromium/media/IDialogSurfaceHolder.aidl
diff --git a/media/base/android/java/src/org/chromium/media/IDialogSurfaceHolder.aidl b/media/base/android/java/src/org/chromium/media/IDialogSurfaceHolder.aidl
index 9f7360400f109843d37d7625a3d969d3acf75e2d..35954c8b8cb7f33676c49ce0ffdb34240d8ea30d 100644
--- a/media/base/android/java/src/org/chromium/media/IDialogSurfaceHolder.aidl
+++ b/media/base/android/java/src/org/chromium/media/IDialogSurfaceHolder.aidl
@@ -22,7 +22,10 @@ interface IDialogSurfaceHolder {
     void scheduleLayoutSurface(int x, int y, int width, int height);
 
     /**
-     * Callback for the activty mapper with the window token or null.
+     * Callback for the activty mapper with the window token or null.  This may
+     * be called back multiple times by the activity mapper as the token is
+     * changed.  Switching tabs between activities is an example of why the
+     * token might change.
      */
     void onWindowToken(IBinder token);
 }