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This is a re-land after first version (r202580) was reverted. The problem was
that extra invalidations occurred due to a call to SetNeedsCommit(). The
solution is to avoid calling SetNeedsCommit(), and accept that this debug info
will be stale on the impl-thread until something else commits.

BUG=240946

Review URL: https://chromiumcodereview.appspot.com/16023024

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202848 0039d316-1c4b-4281-b951-d872f2087c98