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 b0fb4d901fb92e8ed558d87aae138a9a41597c2b..21d851c4e08f73d52698842a9843b05bc212dd23 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -190,7 +190,6 @@ 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;
@@ -223,6 +222,9 @@ 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;