Fix cancelling of device enumeration requests.

content/browser/renderer_host/media/media_stream_dispatcher_host.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/renderer_host/media/media_stream_dispatcher_host.h"
 
 #include "content/browser/browser_main_loop.h"
 #include "content/browser/renderer_host/media/web_contents_capture_util.h"
 #include "content/common/media/media_stream_messages.h"
 #include "content/common/media/media_stream_options.h"
@@ skipping 77 matching lines @@
     const IPC::Message& message, bool* message_was_ok) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP_EX(MediaStreamDispatcherHost, message, *message_was_ok)
     IPC_MESSAGE_HANDLER(MediaStreamHostMsg_GenerateStream, OnGenerateStream)
     IPC_MESSAGE_HANDLER(MediaStreamHostMsg_CancelGenerateStream,
                         OnCancelGenerateStream)
     IPC_MESSAGE_HANDLER(MediaStreamHostMsg_StopStreamDevice,
                         OnStopStreamDevice)
     IPC_MESSAGE_HANDLER(MediaStreamHostMsg_EnumerateDevices,
                         OnEnumerateDevices)
+    IPC_MESSAGE_HANDLER(MediaStreamHostMsg_CancelEnumerateDevices,
+                        OnCancelEnumerateDevices)
     IPC_MESSAGE_HANDLER(MediaStreamHostMsg_OpenDevice,
                         OnOpenDevice)
     IPC_MESSAGE_HANDLER(MediaStreamHostMsg_CloseDevice,
                         OnCloseDevice)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP_EX()
   return handled;
 }
 
 void MediaStreamDispatcherHost::OnChannelClosing() {
@@ skipping 77 matching lines @@
   StoreRequest(render_view_id, page_request_id, label);
 }
 
 void MediaStreamDispatcherHost::OnCancelEnumerateDevices(
     int render_view_id,
     const std::string& label) {
   DVLOG(1) << "MediaStreamDispatcherHost::OnCancelEnumerateDevices("
            << render_view_id << ", "
            << label << ")";
 
+  if (streams_.find(label) == streams_.end()) {
+    // According to the comments in MediaStreamDispatcher::OnDevicesEnumerated,
+    // OnCancelEnumerateDevices can be called several times with the same label.
+    DVLOG(1) << "Enumeration request with label " << label
+             << "does not exist.";
+    return;
+  }
   media_stream_manager_->CancelRequest(label);
   PopRequest(label);
 }
 
 void MediaStreamDispatcherHost::OnOpenDevice(
     int render_view_id,
     int page_request_id,
     const std::string& device_id,
     MediaStreamType type,
     const GURL& security_origin) {
@@ skipping 32 matching lines @@
 MediaStreamDispatcherHost::StreamRequest
 MediaStreamDispatcherHost::PopRequest(const std::string& label) {
   StreamMap::iterator it = streams_.find(label);
   CHECK(it != streams_.end());
   StreamRequest request = it->second;
   streams_.erase(it);
   return request;
 }
 
 }  // namespace content