Make FrameSinkManagerHost usable from //ui/compositor.

The current location of FrameSinkManagerHost won't work if we want to
replace SurfaceManager with FrameSinkManagerHost. SurfaceManager is used
by //ui/compositor which cannot depend on //content/browser.

Move FrameSinkManagerHost to a new component in //components/viz/host.
Also move the singleton that provides a GetFrameSinkManagerHost()
function from ImageTransportFactory to ContextFactoryPrivate.

Bug: 657959
Change-Id: Ib1e9087e9acba2603a67ea478a7ad398730cbbb6
Reviewed-on: https://chromium-review.googlesource.com/521765
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: kylechar <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#477284}

• components/viz/host/BUILD.gn[Added - diff]
• components/viz/host/DEPS[Added - diff]
• components/viz/host/OWNERS[Added - diff]
• components/viz/host/frame_sink_manager_host.cc[Renamed from content/browser/compositor/frame_sink_manager_host.cc - diff]
• components/viz/host/frame_sink_manager_host.h[Renamed from content/browser/compositor/frame_sink_manager_host.h - diff]
• components/viz/host/frame_sink_observer.h[Renamed from content/browser/compositor/frame_sink_observer.h - diff]
• components/viz/host/viz_host_export.h[Added - diff]
• content/browser/BUILD.gn[diff]
• content/browser/compositor/OWNERS[diff]
• content/browser/compositor/gpu_process_transport_factory.cc[diff]
• content/browser/compositor/gpu_process_transport_factory.h[diff]
• content/browser/compositor/image_transport_factory.h[diff]
• content/browser/compositor/surface_utils.cc[diff]
• content/browser/compositor/surface_utils.h[diff]
• content/browser/compositor/test/no_transport_image_transport_factory.cc[diff]
• content/browser/compositor/test/no_transport_image_transport_factory.h[diff]
• content/browser/renderer_host/compositor_impl_android.cc[diff]
• content/browser/renderer_host/compositor_impl_android.h[diff]
• content/browser/renderer_host/offscreen_canvas_provider_impl_unittest.cc[diff]
• content/browser/renderer_host/offscreen_canvas_surface_impl.cc[diff]
• content/browser/renderer_host/offscreen_canvas_surface_impl.h[diff]
• content/test/BUILD.gn[diff]
• ui/aura/BUILD.gn[diff]
• ui/aura/demo/DEPS[diff]
• ui/aura/demo/demo_main.cc[diff]
• ui/compositor/BUILD.gn[diff]
• ui/compositor/DEPS[diff]
• ui/compositor/compositor.h[diff]
• ui/compositor/test/context_factories_for_test.cc[diff]
• ui/compositor/test/in_process_context_factory.cc[diff]
• ui/compositor/test/in_process_context_factory.h[diff]
• ui/views/examples/BUILD.gn[diff]
• ui/views/examples/DEPS[diff]
• ui/views/examples/examples_main.cc[diff]