Convert usages of mojo::ErrorHandler in //device to callbacks.

device/devices_app/devices_app.h

Index: device/devices_app/devices_app.h
diff --git a/device/devices_app/devices_app.h b/device/devices_app/devices_app.h
index eda8d4c98001e3505aaaa1f7e84edeab3a56229d..cac12f4d7fcf9dc11b80e4c0e0b9e7c66372a4fe 100644
--- a/device/devices_app/devices_app.h
+++ b/device/devices_app/devices_app.h
@@ -11,7 +11,6 @@
 #include "base/memory/scoped_ptr.h"
 #include "mojo/application/public/cpp/application_delegate.h"
 #include "mojo/application/public/cpp/interface_factory.h"
-#include "third_party/mojo/src/mojo/public/cpp/bindings/error_handler.h"
 
 namespace base {
 class SequencedTaskRunner;
@@ -28,8 +27,7 @@ class DeviceManager;
 }
 
 class DevicesApp : public mojo::ApplicationDelegate,
-                   public mojo::InterfaceFactory<usb::DeviceManager>,
-                   public mojo::ErrorHandler {
+                   public mojo::InterfaceFactory<usb::DeviceManager> {
  public:
   explicit DevicesApp(
       scoped_refptr<base::SequencedTaskRunner> service_task_runner);
@@ -48,8 +46,8 @@ class DevicesApp : public mojo::ApplicationDelegate,
   void Create(mojo::ApplicationConnection* connection,
               mojo::InterfaceRequest<usb::DeviceManager> request) override;
 
-  // mojo::ErrorHandler:
-  void OnConnectionError() override;
+  // Mojo error handler to track device manager count.
+  void OnConnectionError();
 
   // Sets the app for destruction after a period of idle time. If any top-level
   // services (e.g. usb::DeviceManager) are bound before the timeout elapses,