Fixes android stack tool.

Some logs may contain an empy file, which then gets converted
to a directory.
Test that the symbol file is actually a file.

BUG=341979

Review URL: https://codereview.chromium.org/157913002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249899 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249899
Handle Left out paths on Android/Aura for Async ReadBack.


BUG=323150

Review URL: https://codereview.chromium.org/146873002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249900 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249900