Remove EnableZygote API.

EnableZygote exposes an implementation detail. The utility process
already has a DisableSandbox method, and a SetExposedDir method
that we can use to disable the zygote.

BUG=None
TEST=browser_tests, launch Chrome and install an extension.

Review URL: https://codereview.chromium.org/55133005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232906 0039d316-1c4b-4281-b951-d872f2087c98
[chromedriver] Bump version to 2.6

NOTRY=true

Review URL: https://codereview.chromium.org/57933003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232907 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232906
Add UMA histogram for suppressed dialogs on prerender swap.

Get statistics on how often OnCloseWebContentsDeleter would have showed a
dialog, presumably for onbeforeunload, just to see how often this actually
occurs.

BUG=304932

Review URL: https://codereview.chromium.org/58053002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232908 0039d316-1c4b-4281-b951-d872f2087c98
[Android WebView] Only throttle fallback tick

When throttling, either when paused or when in background, only throttle
fallback tick. There are apps relying on the fact that invalidates are
not throttled when paused. When in background, framework should take
care of not calling back with draw for invalidates.

Internal bug b/11230312

BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/58483002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232909 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232908
SVN changes up to revision 232909