viz: Use a simple GpuMemoryBufferManager implementation.

Introduce InProcessGpuMemoryBufferManager, which directly interacts
with a GpuMemoryBufferFactory to allocate memory used by the display
compositor.

Follow on steps: relocate ServerGpuMemoryBufferManager into viz/host.

BUG=733482

Review-Url: https://codereview.chromium.org/2942283002
Cr-Commit-Position: refs/heads/master@{#481231}
9 files changed