[Pepper] Wire up append mode writing support of FileIO

BUG=334171

Review URL: https://codereview.chromium.org/130053003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247504 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247504
Enable sticky keys by default for launch in M34.

BUG=256946
TEST=manually checked chrome://settings for sticky keys checkbox

Review URL: https://codereview.chromium.org/148163005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247506 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247506