This patch moves the robust resource init logic to the GL front-end.
Instead of initializing texture resources immediately on creation in
D3D11, it defers the clear until before a draw call in some cases, or
skips the update if we can determine if a texture (or other resource)
has been fully initialized.

Currently lazy init is only implemented for Textures, Renderbuffers,
and Surfaces.

Various places where lazy resource init is triggered:
* Framebuffer operations (Draw, Blit, CopyTexImage, Clear, ReadPixels)
* Texture operations (SubImage, GenerateMipmap, CopyTexImage)

Some efficiency gains remain to be implemented, such as when a
SubImage call fills the entire object. Similarly for Blit, and a few
other operations. In these cases we can skip lazy init as an
optimization. Edge cases with EGLImage are mostly untested.

BUG=angleproject:2107

Change-Id: I2bf3a69b1eae0d4feeb5b17daca23451f1037be8
Reviewed-on: https://chromium-review.googlesource.com/576058
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>