Add GetSurfaceManager to ui::ContextFactory.

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index d41a1d7f2c30d5ec2dcdb145405f23240a0867a6..b096551d10e245fc1d6ac0c9c87434bbb2a212e3 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -44,6 +44,7 @@ class LayerTreeHost;
 class RendererSettings;
 class SharedBitmapManager;
 class SurfaceIdAllocator;
+class SurfaceManager;
 class TaskGraphRunner;
 }
 
@@ -116,6 +117,9 @@ class COMPOSITOR_EXPORT ContextFactory {
   virtual std::unique_ptr<cc::SurfaceIdAllocator>
   CreateSurfaceIdAllocator() = 0;
 
+  // Gets the surface manager.
+  virtual cc::SurfaceManager* GetSurfaceManager() = 0;
+
   // Resize the display corresponding to this compositor to a particular size.
   virtual void ResizeDisplay(ui::Compositor* compositor,
                              const gfx::Size& size) = 0;