Add UpdateImpl, it seems to be required by the new ContentHost stuff even though we're double-buffered here
GrallocTextureHostOGL improvements/fixes; Revert BindExternalBuffer to its original crappiness with comments
Open read-only the surfaces that we're only going to access for read. Fixes genlock failures on B2G as genlock write locks are exclusive with any other lock.
fix trivial compile error that I just introduced