cc: Convert some LTHCommon "TransformsFor" tests
cc: Convert some LTHCommon "TransformsFor" tests

Converts these tests from using Layers to using LayerImpls so that
values that they are looking that should only appear on the compositor
thread can keep working.

Tests:
    LayerTreeHostCommonTest.TransformsForFlatteningLayer
    LayerTreeHostCommonTest.TransformsForRenderSurfaceHierarchy
    LayerTreeHostCommonTest.TransformsForReplica
    LayerTreeHostCommonTest.TransformsForSingleRenderSurface

R=weiliangc@chromium.org
BUG=504466,50241
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1253103004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#340484}

CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend