Presentation API: implement .getAvailability() (Chromium side).

content/renderer/presentation/presentation_dispatcher.h

Index: content/renderer/presentation/presentation_dispatcher.h
diff --git a/content/renderer/presentation/presentation_dispatcher.h b/content/renderer/presentation/presentation_dispatcher.h
index 4642a644ba19899a626ce3a0db05f8e070d277cf..2dbf07c3f1387b0d1b7f34bf4c3d39a4221eda57 100644
--- a/content/renderer/presentation/presentation_dispatcher.h
+++ b/content/renderer/presentation/presentation_dispatcher.h
@@ -6,6 +6,7 @@
 #define CONTENT_RENDERER_PRESENTATION_PRESENTATION_DISPATCHER_H_
 
 #include "base/compiler_specific.h"
+#include "base/id_map.h"
 #include "base/memory/linked_ptr.h"
 #include "content/common/content_export.h"
 #include "content/common/presentation/presentation_service.mojom.h"
@@ -13,6 +14,7 @@
 #include "third_party/WebKit/public/platform/modules/presentation/WebPresentationClient.h"
 
 namespace blink {
+class WebPresentationAvailabilityObserver;
 class WebString;
 }  // namespace blink
 
@@ -58,6 +60,11 @@ class CONTENT_EXPORT PresentationDispatcher
   virtual void closeSession(
       const blink::WebString& presentationUrl,
       const blink::WebString& presentationId);
+  virtual void getAvailability(
+      const blink::WebString& presentationUrl,
+      blink::WebPresentationAvailabilityCallbacks* callbacks);
+  virtual void startListening(blink::WebPresentationAvailabilityObserver*);
+  virtual void stopListening(blink::WebPresentationAvailabilityObserver*);
 
   // RenderFrameObserver implementation.
   void DidChangeDefaultPresentation() override;
@@ -84,6 +91,8 @@ class CONTENT_EXPORT PresentationDispatcher
 
   void ConnectToPresentationServiceIfNeeded();
 
+  void UpdateListeningState();
+
   // Used as a weak reference. Can be null since lifetime is bound to the frame.
   blink::WebPresentationController* controller_;
   presentation::PresentationServicePtr presentation_service_;
@@ -95,6 +104,23 @@ class CONTENT_EXPORT PresentationDispatcher
       std::queue<linked_ptr<presentation::SessionMessage>>;
   MessageRequestQueue message_request_queue_;
 
+  enum class ListeningState {
+    Inactive,
+    Waiting,
+    Active,
+  };
+
+  ListeningState listening_state_;
+  bool last_known_availability_;
+
+  using AvailabilityCallbacksMap =
+      IDMap<blink::WebPresentationAvailabilityCallbacks, IDMapOwnPointer>;
+  AvailabilityCallbacksMap availability_callbacks_;
+
+  using AvailabilityObserversSet =
+      std::set<blink::WebPresentationAvailabilityObserver*>;
+  AvailabilityObserversSet availability_observers_;
+
   DISALLOW_COPY_AND_ASSIGN(PresentationDispatcher);
 };