GitLab

Create a viz::ToMTLPixelFormat helper function, and use it in the
shared image factory, and in the output surface allocation.

Update the default gfx::BufferFormat for SkiaOutputDeviceBufferQueue
for macOS, and add a TODO noting that the correct value should be
determined at the Reshape call, and not at initialization.

This is enough to get --enable-features=SkiaRenderer,Metal to draw
the browser and some simple pages.

Bug: 894929
Change-Id: I3fde39349fecaea856293609e5b877c49e46d0e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2225485
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774843}