[Android] Revert some code about file picker.

This patch is to revert some code about file picker.
If the app client does not declare content provider and file path
of image was used, file picker will not work.
Related list of Chromium CLs:
   https://codereview.chromium.org/489053003
   https://codereview.chromium.org/591253002

BUG=XWALK-2631, XWALK-2717