Support cancellation of request for opening device.

content/renderer/media/media_stream_dispatcher.cc

Index: content/renderer/media/media_stream_dispatcher.cc
===================================================================
--- content/renderer/media/media_stream_dispatcher.cc	(revision 209718)
+++ content/renderer/media/media_stream_dispatcher.cc	(working copy)
@@ -85,18 +85,21 @@
                                              security_origin));
 }
 
-void MediaStreamDispatcher::CancelGenerateStream(int request_id) {
+void MediaStreamDispatcher::CancelGenerateStream(
+    int request_id,
+    const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler) {
   DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::CancelGenerateStream"
            << ", {request_id = " << request_id << "}";
 
   RequestList::iterator it = requests_.begin();
   for (; it != requests_.end(); ++it) {
-    Request& request = *it;
-    if (request.request_id == request_id) {
+    if (it->request_id == request_id &&
+        it->handler.get() == event_handler.get()) {

[tommi (sloooow) - chröme, 2013/07/03 08:05:12]

is this the right thing to do?  it seems to me that canceling a request with a
specific ID should always cancel that request.
Is it possible perhaps that there be more than one request with the same ID? 
(if so, this needs to be documented)

[wjia(left Chromium), 2013/07/03 17:41:36]

Yes, it's the right thing to do. The request_id is created by each client and
there could be multiple clients, e.g., MediaStreamImpl and
PepperPluginDelegateImpl. Each client should guarantee its request_id is unique
within that handler. 

When MediaStreamDispatcher receives a request, it will map pair (request_id,
handler) to a unique ipc_request. 

+      int ipc_request = it->ipc_request;
       requests_.erase(it);
       Send(new MediaStreamHostMsg_CancelGenerateStream(routing_id(),
-                                                       request_id));
+                                                       ipc_request));
       break;
     }
   }
@@ -197,6 +200,12 @@
                                          security_origin));
 }
 
+void MediaStreamDispatcher::CancelOpenDevice(
+    int request_id,
+    const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler) {
+  CancelGenerateStream(request_id, event_handler);
+}
+
 void MediaStreamDispatcher::CloseDevice(const std::string& label) {
   DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::CloseDevice"