WebGL: Don't call unnecessary glConsumeTexture.

The recycle mailbox was created by the WebGL context, so it is not necessary to
call glConsumeTexture. For the same reason, Canvas2DLayerBridge also reuses
mailboxs without calling glConsumeTexture.

BUG=332401

Review URL: https://codereview.chromium.org/159783003

git-svn-id: svn://svn.chromium.org/blink/trunk@167006 bbb929c8-8fbe-4397-9dbb-9b2b20218538