cc: Move worker threads to RenderThreadImpl.

This allows us to Join the threads when RenderThreadImpl
is shutdown.

BUG=468785
TEST=cc_unittests

Review URL: https://codereview.chromium.org/999173004

Cr-Commit-Position: refs/heads/master@{#321836}

• android_webview/browser/hardware_renderer.cc[diff]
• cc/BUILD.gn[diff]
• cc/animation/scrollbar_animation_controller_linear_fade_unittest.cc[diff]
• cc/animation/scrollbar_animation_controller_thinning_unittest.cc[diff]
• cc/cc_tests.gyp[diff]
• cc/debug/micro_benchmark_controller_unittest.cc[diff]
• cc/input/top_controls_manager_unittest.cc[diff]
• cc/layers/delegated_renderer_layer_impl_unittest.cc[diff]
• cc/layers/heads_up_display_layer_impl_unittest.cc[diff]
• cc/layers/layer_impl_unittest.cc[diff]
• cc/layers/layer_perftest.cc[diff]
• cc/layers/layer_position_constraint_unittest.cc[diff]
• cc/layers/layer_unittest.cc[diff]
• cc/layers/layer_utils_unittest.cc[diff]
• cc/layers/picture_image_layer_impl_unittest.cc[diff]
• cc/layers/picture_layer.cc[diff]
• cc/layers/picture_layer_impl_perftest.cc[diff]
• cc/layers/picture_layer_impl_unittest.cc[diff]
• cc/layers/picture_layer_unittest.cc[diff]
• cc/layers/render_surface_unittest.cc[diff]
• cc/layers/scrollbar_layer_unittest.cc[diff]
• cc/layers/solid_color_layer_impl_unittest.cc[diff]
• cc/layers/texture_layer_unittest.cc[diff]
• cc/layers/tiled_layer_impl_unittest.cc[diff]
• cc/layers/tiled_layer_unittest.cc[diff]
• cc/resources/display_list_recording_source.cc[diff]
• cc/resources/display_list_recording_source.h[diff]
• cc/resources/picture_pile.cc[diff]
• cc/resources/picture_pile.h[diff]
• cc/resources/recording_source.h[diff]
• cc/resources/tile_manager_perftest.cc[diff]
• cc/resources/tile_manager_unittest.cc[diff]
• cc/resources/tile_task_worker_pool.cc[diff]
• cc/resources/tile_task_worker_pool.h[diff]
• cc/resources/tile_task_worker_pool_unittest.cc[diff]
• cc/test/fake_layer_tree_host.cc[diff]
• cc/test/fake_layer_tree_host_impl.cc[diff]
• cc/test/fake_layer_tree_host_impl.h[diff]
• cc/test/fake_ui_resource_layer_tree_host_impl.cc[diff]
• cc/test/layer_tree_json_parser_unittest.cc[diff]
• cc/test/layer_tree_pixel_resource_test.cc[diff]
• cc/test/layer_tree_test.cc[diff]
• cc/test/layer_tree_test.h[diff]
• cc/test/test_task_graph_runner.cc[Added - diff]
• cc/test/test_task_graph_runner.h[Added - diff]
• cc/trees/damage_tracker_unittest.cc[diff]
• cc/trees/layer_tree_host.cc[diff]
• cc/trees/layer_tree_host.h[diff]
• cc/trees/layer_tree_host_common_unittest.cc[diff]
• cc/trees/layer_tree_host_impl.cc[diff]
• cc/trees/layer_tree_host_impl.h[diff]
• cc/trees/layer_tree_host_impl_unittest.cc[diff]
• cc/trees/layer_tree_host_unittest.cc[diff]
• cc/trees/layer_tree_host_unittest_no_message_loop.cc[diff]
• cc/trees/layer_tree_host_unittest_scroll.cc[diff]
• cc/trees/layer_tree_impl_unittest.cc[diff]
• cc/trees/layer_tree_settings.cc[diff]
• cc/trees/layer_tree_settings.h[diff]
• cc/trees/occlusion_tracker_perftest.cc[diff]
• cc/trees/tree_synchronizer_unittest.cc[diff]
• content/browser/compositor/gpu_process_transport_factory.cc[diff]
• content/browser/compositor/gpu_process_transport_factory.h[diff]
• content/browser/renderer_host/compositor_impl_android.cc[diff]
• content/renderer/gpu/compositor_dependencies.h[diff]
• content/renderer/gpu/render_widget_compositor.cc[diff]
• content/renderer/render_thread_impl.cc[diff]
• content/renderer/render_thread_impl.h[diff]
• content/test/fake_compositor_dependencies.cc[diff]
• content/test/fake_compositor_dependencies.h[diff]
• content/test/web_layer_tree_view_impl_for_testing.cc[diff]
• mojo/services/html_viewer/weblayertreeview_impl.cc[diff]
• ui/compositor/compositor.cc[diff]
• ui/compositor/compositor.h[diff]
• ui/compositor/test/in_process_context_factory.cc[diff]
• ui/compositor/test/in_process_context_factory.h[diff]