Add a metric to measure the keyboard load time.

This involves adding a new extension api that's a callback called by the Keyboard code when all keyboard elements are loaded. This can be used for other purposes in the future, such as allowing the ash/aura side to show a loading animation, or handle showing of the keyboard differently.

BUG=265326
TEST=Start Chrome OS and focus on a text box and wait for the keyboard to appear. Then go to chrome://histograms and ensure that Keyboard.FirstLoadTime appears and the measurement is roughly how long it took for the keyboard to fully appear after focusing the text box.

Review URL: https://codereview.chromium.org/37213002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231225 0039d316-1c4b-4281-b951-d872f2087c98
Disable delegated rendering in content_shell --dump-render-tree.

With delegated rendering enabled in Win Aura, all pixel test dumping is broken.

R=jamesr@chromium.org, piman@chromium.org, jochen@chromium.org
BUG=311404

Review URL: https://codereview.chromium.org/42493002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231226 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231226
Update V8 to version 3.22.22.

TBR=danno@chromium.org

Review URL: https://codereview.chromium.org/43333005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231227 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231228 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231227
SVN changes up to revision 231228