Assign unique partition ID to gaia webview

every gaia webview should always have its own clean and isolated cookie jar. This will fix the bug that when a user signs in to chrome and then tries to add a secondary account to the profile in the same browser session, the embedded gaia webview will show a reauth page instead of a sign in page.

BUG=

Review URL: https://codereview.chromium.org/45463004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233456 0039d316-1c4b-4281-b951-d872f2087c98
Add ExternalPrerenderRequestHandler and related API

This class will be used to handle prerender requests coming from external applications.
For better tracking and also supportig referrer, a separate PrerenderManager API is
added.

BUG=297859

Review URL: https://codereview.chromium.org/45693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233457 0039d316-1c4b-4281-b951-d872f2087c98
[rAC, OSX] Use bubble windows for error messages.

In the short term, this addresses the issue of messages that are too long
to fit in the dialog - the window will extend outside the dialog. In the
long run, this also prepares for further changes around the error bubble
that do require the BaseBubble machinery.

R=rsesek@chromium.org
BUG=308200

Review URL: https://codereview.chromium.org/49063012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233458 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233457
Replace dependance on /home/chronos/user with cryptohome-path.

BUG=314733
TEST=manual
NOTRY=True

Review URL: https://codereview.chromium.org/59353002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233459 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233459