D3D11: Re-enable updateVertexBuffer dirty bits. In some cases, when the app would call glBufferSubData to do a small data update in an existing vertex buffer, the sync code would not flush out the data to the native D3D11 buffer from the temporary staging buffer. Fix this problem by notifying the VertexArray11 class when buffer data is updated. Note that in the future we can improve this by using a different update notification for when the buffer data changes and when the underlying storage changes. For now take a very broad approach. BUG=angleproject:1156 Change-Id: I2e0fabc97c1f1d5a14d609247e61c602e9a5a85f Reviewed-on: https://chromium-review.googlesource.com/644208 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>