Chromium plumbing for Screen Orientation API lock/unlock.

content/browser/screen_orientation/screen_orientation_dispatcher_host.h

Index: content/browser/screen_orientation/screen_orientation_dispatcher_host.h
diff --git a/content/browser/screen_orientation/screen_orientation_dispatcher_host.h b/content/browser/screen_orientation/screen_orientation_dispatcher_host.h
index 75620d9738d7db0959f6d2e47d2831960954fade..45ec7164fa59dd1b1b0d8ddc4b2962817cc21d85 100644
--- a/content/browser/screen_orientation/screen_orientation_dispatcher_host.h
+++ b/content/browser/screen_orientation/screen_orientation_dispatcher_host.h
@@ -10,8 +10,13 @@
 
 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();
 
@@ -20,9 +25,17 @@ class ScreenOrientationDispatcherHost : public BrowserMessageFilter {
 
   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.

 };