Remove GetSharedMainThreadContextProvider from CompositorDependencies.

content/test/fake_compositor_dependencies.h

Index: content/test/fake_compositor_dependencies.h
diff --git a/content/test/fake_compositor_dependencies.h b/content/test/fake_compositor_dependencies.h
index 5aa31e727445a2925af996289c21050f8d5883f0..5198ed1416add0150e2e164ec59327edbc310b25 100644
--- a/content/test/fake_compositor_dependencies.h
+++ b/content/test/fake_compositor_dependencies.h
@@ -37,7 +37,6 @@ class FakeCompositorDependencies : public CompositorDependencies {
   cc::SharedBitmapManager* GetSharedBitmapManager() override;
   gpu::GpuMemoryBufferManager* GetGpuMemoryBufferManager() override;
   scheduler::RendererScheduler* GetRendererScheduler() override;
-  cc::ContextProvider* GetSharedMainThreadContextProvider() override;
   std::unique_ptr<cc::BeginFrameSource> CreateExternalBeginFrameSource(
       int routing_id) override;
   cc::ImageSerializationProcessor* GetImageSerializationProcessor() override;