Convert USE(NATIVE_FULLSCREEN_VIDEO) to a runtime enabled feature

This patch adds the boilerplate code to propagate command line switch to Blink,
and selectively enables alpha channel in content_shell for layout tests.

Blink patch: https://codereview.chromium.org/22454003

R=jam@chromium.org

Review URL: https://codereview.chromium.org/23597036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225412 0039d316-1c4b-4281-b951-d872f2087c98
[rAc] Fetch username concurrently with fetching Wallet items.

BUG=270859
TEST=Autofill dialog should still work correctly, but a little bit faster.
R=groby@chromium.org

Review URL: https://codereview.chromium.org/23653052

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225413 0039d316-1c4b-4281-b951-d872f2087c98
Remove the OverscrollGlow when not needed

OverscrollGlow has 8 layers attached to it that
don't draw most of the time. This CL removes
the OverscrollGlow from the layer tree when
it's not needed.

BUG=286003

Review URL: https://codereview.chromium.org/24165011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225414 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225413
Add an event filter to log the time between keystrokes.

BUG=292290

TEST=In an Aura enabled version of Chrome, type a bunch of words into the Omnibox. Then visit about:histograms and ensure that a Keyboard.KeystrokeDeltas histogram exists with various values.

Review URL: https://codereview.chromium.org/24409002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225415 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225415