Plumbing explicit share groups through context creation

Requires corresponding Blink changes, which is why the new interfaces are hidden
behind #ifdefs.

BUG=127940
R=kbr@chromium.org, piman@chromium.org, sievers@chromium.org

Review URL: https://codereview.chromium.org/101223005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253204 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253204
Fix stale reinit in the shader translator.

In some cases we would initialize, free, then re-initialize the
shader translator within the same initialized memory. The local
static tracking initialization would get stuck and we would fail
on subsequent calls. We can fix this by using a non-local static.

We ran into this problem in some unit tests which use the
in-process GPU, likely because of the single-process model.

BUG=344043
R=zmo@chromium.org, jbauman@chromium.org

Review URL: https://codereview.chromium.org/178043002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253205 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253206 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253206