Chromium plumbing for Screen Orientation API lock/unlock.

content/browser/screen_orientation/screen_orientation_dispatcher_host.h

 // Copyright 2014 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 CONTENT_BROWSER_SCREEN_ORIENTATION_DISPATCHER_HOST_H_
 #define CONTENT_BROWSER_SCREEN_ORIENTATION_DISPATCHER_HOST_H_
 
 #include "content/public/browser/browser_message_filter.h"
 #include "third_party/WebKit/public/platform/WebScreenOrientation.h"
 
 namespace content {
 
-// ScreenOrientationDispatcherHost
-class ScreenOrientationDispatcherHost : public BrowserMessageFilter {
+class ScreenOrientationProvider;
+
+// ScreenOrientationDispatcherHost is a browser filter for Screen Orientation
+// messages and also helps dispatching messages about orientation changes to the
+// renderers.
+class CONTENT_EXPORT ScreenOrientationDispatcherHost
+    : public BrowserMessageFilter {
  public:
   ScreenOrientationDispatcherHost();
 
   // BrowserMessageFilter
   virtual bool OnMessageReceived(const IPC::Message&, bool*) OVERRIDE;
 
   void OnOrientationChange(blink::WebScreenOrientation orientation);
 
-private:
-  virtual ~ScreenOrientationDispatcherHost() {}
+  void SetProviderForTests(ScreenOrientationProvider* provider);
 
+ private:
+  virtual ~ScreenOrientationDispatcherHost();
+
+  void OnLockRequest(blink::WebScreenOrientations orientations);
+  void OnUnlockRequest();
+
+  static ScreenOrientationProvider* CreateProvider();
+
+  scoped_ptr<ScreenOrientationProvider> provider_;

[jochen (gone - plz use gerrit), 2014/02/25 16:23:06]

with this design, you will have one provider per process. How do they sync lock
requests?

Have you considered a design similar to geolocation, where the provider is a
singleton?

Could you first add the provider, and then the plumbing? That will make
reviewing easier.

[mlamouri (slow - plz ping), 2014/02/28 11:53:30]

I think for the moment, the only requirement we have is that a flow of
lock/unlock calls should arrive to the provider at the same speed as 
Geolocation is considered as an anti-pattern nowadays. I am trying to follow a
more modern implementation design like Vibration API which I believe creates a
provider per process.
It sounds unnatural because we want a plumbing that is generic and not linked to
one specific provider, right? Also, given that you are OOO on Monday, I was
hoping that we could land this before ;)

   DISALLOW_COPY_AND_ASSIGN(ScreenOrientationDispatcherHost);

[jochen (gone - plz use gerrit), 2014/02/25 16:23:06]

nit. add empty line before this line

[mlamouri (slow - plz ping), 2014/02/28 11:53:30]

Done.

 };
 
 }  // namespace content
 
 #endif // CONTENT_BROWSER_SCREEN_ORIENTATION_DISPATCHER_HOST_H_