Chromium: add to support file uploading

This change adds function implementation in WebViewContentsClientAdapter
for supporting uploading file in browser. 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: I2dbf6a39e68725b222650755dbf6b6882d4f209d