[Android] Fix the issue about file picker does not work.

This patch is to fix the issue about file picker does not work.
Upstream has added content URI to upload photos taken by camera,
so we follow it.

BUG=XWALK-2631
> App client should supply a content provider to check permission. 
> We can insert the related code about content provider to "AndroidManifest.xml" in customize.py.

AppTemplate is one of the embedders using Embedding API. For other embedders, AndroidManifest is out of our scope. If we can't work around this, please at least make sure it handles well if the app doesn't declare such content provider.