Add PDF compositor service

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 0240ef3517495ba0da69ae6d72ad2761f4e89710..deb435fe31016ef3a29f9cd01eb71efbd008a665 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -193,7 +193,6 @@ class CONTENT_EXPORT RenderThreadImpl
   IPC::SyncChannel* GetChannel() override;
   std::string GetLocale() override;
   IPC::SyncMessageFilter* GetSyncMessageFilter() override;
-  scoped_refptr<base::SingleThreadTaskRunner> GetIOTaskRunner() override;
   void AddRoute(int32_t routing_id, IPC::Listener* listener) override;
   void RemoveRoute(int32_t routing_id) override;
   int GenerateRoutingID() override;
@@ -226,6 +225,9 @@ class CONTENT_EXPORT RenderThreadImpl
       const std::string& name,
       mojo::ScopedInterfaceEndpointHandle handle) override;
 
+  // ChildThread implementation via ChildThreadImpl:
+  scoped_refptr<base::SingleThreadTaskRunner> GetIOTaskRunner() override;
+
   // CompositorDependencies implementation.
   bool IsGpuRasterizationForced() override;
   bool IsAsyncWorkerContextEnabled() override;