[AudioPlayer] Don't start a playback automatically when reopening

This patch is a reland of r254749, fixing a way to set the 'playing' attribute.

BUG=chrome-os-partner:26171
TEST=manually
TBR=hirono@chromium.org

Review URL: https://codereview.chromium.org/182733009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255561 0039d316-1c4b-4281-b951-d872f2087c98
Make delegate_execute GetLaunchMode() check for default browser.

BUG=350078

Review URL: https://codereview.chromium.org/189113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255562 0039d316-1c4b-4281-b951-d872f2087c98
Define the ExtensionId typedef, and use it in extension.h.

This is primarily for documentation now, but one could imagine using a more
efficient representation for this known-length string once everywhere is
converted to use the same type name.

Review URL: https://codereview.chromium.org/189123005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255563 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255562
Implement '--gpu-sandbox-failures-nonfatal' flag.

Also, move the flag to content:: instead of chromeos::.

BUG=327824
TEST=Chrome compiles, loads with and without the flag.

Review URL: https://codereview.chromium.org/189313002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255564 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255564