[Presentation API] 1-UA presentation support + presenter APIs.

content/public/browser/presentation_service_delegate.h

Index: content/public/browser/presentation_service_delegate.h
diff --git a/content/public/browser/presentation_service_delegate.h b/content/public/browser/presentation_service_delegate.h
index 3005609e936722a0eb1051965e1db2446c3e758a..67679eeac5b750d6b1bd11a18c72deee69a2c1b1 100644
--- a/content/public/browser/presentation_service_delegate.h
+++ b/content/public/browser/presentation_service_delegate.h
@@ -26,6 +26,11 @@ class PresentationSessionStateListener;
 using PresentationSessionMessageCallback = base::Callback<
     void(const ScopedVector<content::PresentationSessionMessage>&, bool)>;
 
+using PresentationReceiverSessionAvailableCallback =
+    base::Callback<void(const content::PresentationSessionInfo*)>;
+
+using SendMessageCallback = base::Callback<void(bool)>;
+
 // An interface implemented by embedders to handle presentation API calls
 // forwarded from PresentationServiceImpl.
 class CONTENT_EXPORT PresentationServiceDelegate {
@@ -51,7 +56,6 @@ class CONTENT_EXPORT PresentationServiceDelegate {
       base::Callback<void(const PresentationSessionInfo&)>;
   using PresentationSessionErrorCallback =
       base::Callback<void(const PresentationError&)>;
-  using SendMessageCallback = base::Callback<void(bool)>;
 
   virtual ~PresentationServiceDelegate() {}
 
@@ -179,6 +183,28 @@ class CONTENT_EXPORT PresentationServiceDelegate {
       int render_process_id,
       int render_frame_id,
       content::PresentationSessionStateListener* listener) = 0;
+
+  // Gets a receiver presentation session for the offscreen presentation hosted

[miu, 2015/10/07 21:51:47]

The wording in this comment was a bit confusing to me.  How about:

  Runs |callback| once the receiver becomes available.  |callback| may be run
during this method call (if the receiver is already available), or at some later
time.  |render_process_id| and |render_frame_id| must refer to the main render
frame of an off-screen tab.

BTW--What should happen if a receiver never becomes available?  Is the callback
guaranteed to be run with a nullptr, or never run at all?

[imcheng, 2015/10/10 04:39:44]

Done. If a receiver session never becomes available, the callback will never be
run.

+  // on the offscreen tab containing this frame, or waits until one is
+  // available.
+  // If there is at least one receiver presentation session, |callback| will
+  // be invoked with one of the sessions immediately.
+  // Otherwise, |callback| will be invoked when a receiver presentation session
+  // becomes available.
+  // If the calling frame is not the main frame of an offscreen tab,
+  // |callback| will be invoked with null.
+  virtual void GetPresentationReceiverSession(

[miu, 2015/10/07 21:51:47]

Consider naming this method something like
NotifyWhenReceiverSessionIsAvailable() to make it clear that it's different from
GetPresentationReceiverSessions().

Even better, consider eliminating this method (and ListenForSessionMessages()
and ListenForSessionStateChange()) by adding extra methods to the Observer
interface.  Then, you also won't need all these extra callback typedefs.

[imcheng, 2015/10/10 04:39:44]

Renamed per your suggestion. I am not a fan of the
PresentationServiceDelegate::Observer interface. I think it's clearer to define
the expected behavior yet rather than having an all purpose observer class.

+      int render_process_id,
+      int render_frame_id,
+      const PresentationReceiverSessionAvailableCallback& callback) = 0;
+
+  // Gets all receiver presentation sessions for the offscreen presentation
+  // hosted on the offscreen tab containing this frame.
+  // If the calling frame is not the main frame of an offscreen tab, an empty
+  // vector will be returned.
+  virtual std::vector<content::PresentationSessionInfo>
+  GetPresentationReceiverSessions(int render_process_id,
+                                  int render_frame_id) = 0;
 };
 
 }  // namespace content