GitLab

Split GpuMode::HARDWARE_ACCELERATED into HARDWARE_GL, HARDWARE_VULKAN,
and HARDWARE_METAL. Then, during GpuDataManagerImpl initialization, add
GL to the |fallback_modes_| stack, followed by Vulkan or Metal if they
are enabled.

GL can still be used in the Vulkan and Metal modes, but disable Vulkan
and Metal when the GPU is not running in that mode. This way, the first
GPU fallback will still leave hardware acceleration available.

Note that this doesn't check what Vulkan or Metal are being used for.
For instance, with the flag --use-vulkan=native, Vulkan will be
initialized, but Skia GL will still be used for compositing without the
flag --enable-features=Vulkan. In this case, the first fallback will
disable Vulkan anyway, and the second will disable GL.

Bug: 1005383
Change-Id: I2cc46b4861f325883f8324bde541410440764c3c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1976827
Commit-Queue: Sean Gilhuly <sgilhuly@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734192}