android_webview: add to support file uploading

This commit changes function from empty implementation
to abstract function interface in AwContentsClient for
supporting uploading file in browser. Its subclass will
override this function. In Android 4.4, browser is based
on chromium not webkit engine, chromium engine support
uploading file and will callback to client to show file
chooser, but android_webview client has empty
implementation within this callback for file chooser.

So we solve this issue by adding implementation in framework
chromium client which extends android_webview client, function
in framework webkit client and corresponding functions in
browser app.

Change-Id: I50375573848879f3c30069b1831b314f0c536163
Merge "android_webview: add to support file uploading"
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
Merge "Webview: Release MediaMetadataRetriever after get media info"
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
Merge "Webview: Implement the suspend/resume operation in webview of chromium"
Audio: Request AudioFocus when resume html audio playback

- In html audio suspend state, AudioFocus will be abandoned
  by itself in Suspend(), but when resume playback AudioFocus
  will not be requested. As a result, when start local
  audio playback and request AudioFocus at this time, html
  audio will not be paused and still playback.

- Request AudioFocus when resume html audio playback.

CRs-Fixed: 627121

Change-Id: I8cdc26b6022890718d019c75f19fe2e008b702ed
Merge "Audio: Request AudioFocus when resume html audio playback"