arc: enable Android tracing from chrome://tracing in dev mode

components/arc/arc_bridge_host_impl.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_ARC_ARC_BRIDGE_HOST_IMPL_H_
 #define COMPONENTS_ARC_ARC_BRIDGE_HOST_IMPL_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 53 matching lines @@
   void OnNotificationsInstanceReady(
       mojom::NotificationsInstancePtr notifications_ptr) override;
   void OnObbMounterInstanceReady(
       mojom::ObbMounterInstancePtr obb_mounter_ptr) override;
   void OnPolicyInstanceReady(mojom::PolicyInstancePtr policy_ptr) override;
   void OnPowerInstanceReady(mojom::PowerInstancePtr power_ptr) override;
   void OnPrintInstanceReady(mojom::PrintInstancePtr print_ptr) override;
   void OnProcessInstanceReady(mojom::ProcessInstancePtr process_ptr) override;
   void OnStorageManagerInstanceReady(
       mojom::StorageManagerInstancePtr storage_manager_ptr) override;
+  void OnTracingInstanceReady(mojom::TracingInstancePtr trace_ptr) override;
   void OnTtsInstanceReady(mojom::TtsInstancePtr tts_ptr) override;
   void OnVideoInstanceReady(mojom::VideoInstancePtr video_ptr) override;
   void OnWallpaperInstanceReady(
       mojom::WallpaperInstancePtr wallpaper_ptr) override;
 
  private:
   // Called when the bridge channel is closed. This typically only happens when
   // the ARC instance crashes.
   void OnClosed();
 
@@ skipping 16 matching lines @@
   // Put as a last member to ensure that any callback tied to the elements
   // is not invoked.
   std::vector<std::unique_ptr<MojoChannel>> mojo_channels_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcBridgeHostImpl);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_ARC_BRIDGE_HOST_IMPL_H_