chromium: clear favicon bitmap prior to load an url

Favicon bitmap reference should be clear before every call to loadUrl. Otherway, webclient
reports the incorrect favicon. Xe: Aosp browser display the old favicon if the new page
doesn't have a favicon, because webview.getFavicon() returns the old bitmap (about:blank page
shouldn't have to have a favicon).

Patchset 2: Better bug code's description comment

Change-Id: I9c41e3b240c4453092428b895556b94fb938e06f
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Webview: Release MediaMetadataRetriever after get media info

- MediaResourceGetter create an object of MediaMetadataRetriever,
  in order to get the duration, width, height of the clip.
- After got enough info, the object should be released.
- Especially in streaming, MediaMetadataRetriever will create a
  connection which will require the data continuously in
  background.

Change-Id: I20dc9f4ca7c38fe7968c78c5b8e2274d6864579d
Webview: Implement the suspend/resume operation in webview of chromium

- To use the new APIs (suspend/resume) of MediaPlayer
- Suspend will release the decoders and maintain the cached data for
  http streaming, instead of release the whole player.
- Resume will init the decoders before start() is called.

Change-Id: Iab7a7c8abb00368cb1eb15ba267f92689cc50be3