Move ArcSessionRunner from ArcBridgeService to ArcSessionManager.

components/arc/arc_service_manager.h

Index: components/arc/arc_service_manager.h
diff --git a/components/arc/arc_service_manager.h b/components/arc/arc_service_manager.h
index 68df26a1645e6f2afeb0e768d3fc7ac88ddfab65..81a4ea9e98b2e715e289b112d3cae2660d72cbd6 100644
--- a/components/arc/arc_service_manager.h
+++ b/components/arc/arc_service_manager.h
@@ -21,7 +21,6 @@ namespace arc {
 class ArcBridgeService;
 class ArcIntentHelperObserver;
 class ArcService;
-class ArcSessionRunner;
 
 // Manages creation and destruction of services that communicate with the ARC
 // instance via the ArcBridgeService.
@@ -66,11 +65,6 @@ class ArcServiceManager {
     return blocking_task_runner_;
   }
 
-  // Set ArcSessionRunner instance for testing. Call before ArcServiceManager
-  // creation.
-  static void SetArcSessionRunnerForTesting(
-      std::unique_ptr<ArcSessionRunner> arc_session_runner);
-
   // Returns the icon loader owned by ArcServiceManager and shared by services.
   scoped_refptr<ActivityIconLoader> icon_loader() { return icon_loader_; }