Fix teardown of stale AudioStreamMonitor poll callbacks.

content/browser/media/audio_stream_monitor.cc

 // Copyright 2014 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/media/audio_stream_monitor.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/invalidate_type.h"
 #include "content/public/browser/render_frame_host.h"
 
 namespace content {
 
 namespace {
 
 enum class ActionType { STARTING, STOPPING };
 AudioStreamMonitor* StartStopMonitoringHelper(ActionType action_type,
                                               int render_process_id,
                                               int render_frame_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   // It's important that this code uses only the process id for lookup as there
   // may not be a RenderFrameHost or WebContents attached to the RenderProcess
   // at time of call; e.g., in the event of a crash.

[Charlie Reis, 2017/02/17 21:27:55]

Looks like this was already partly-noted here?  :)  

[DaleCurtis, 2017/02/17 22:03:59]

Yes, but when written I had assumed only the RenderProcessHost was reused, not
the WebContents too :)

   RenderProcessHost* const render_process_host =
       RenderProcessHost::FromID(render_process_id);
   if (!render_process_host)
     return nullptr;
 
   // TODO(dalecurtis, maxmorin): We should really only be sending these when the
   // streams are audible or we don't have power level monitoring.
   if (action_type == ActionType::STARTING)
     render_process_host->OnAudioStreamAdded();
   else
@@ skipping 21 matching lines @@
 bool AudioStreamMonitor::WasRecentlyAudible() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return was_recently_audible_;
 }
 
 bool AudioStreamMonitor::IsCurrentlyAudible() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return is_audible_;
 }
 
+void AudioStreamMonitor::RenderProcessGone(int render_process_id) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  // Note: It's possible for the RenderProcessHost and WebContents (and thus
+  // this class) to survive the death of the render process and subsequently be
+  // reused. During this period StartStopMonitoringHelper() will be unable to
+  // lookup the WebContents using the now-dead |render_frame_id|. We must thus
+  // have this secondary mechanism for clearing stale callbacks.
+
+  for (auto it = poll_callbacks_.begin(); it != poll_callbacks_.end();) {
+    if (it->first.first == render_process_id) {
+      it = poll_callbacks_.erase(it);
+      if (!power_level_monitoring_available())
+        OnStreamRemoved();
+    } else {
+      ++it;
+    }
+  }
+
+  if (poll_callbacks_.empty())
+    poll_timer_.Stop();
+}
+
 // static
 void AudioStreamMonitor::StartMonitoringStream(
     int render_process_id,
     int render_frame_id,
     int stream_id,
     const ReadPowerAndClipCallback& read_power_callback) {
   BrowserThread::PostTask(BrowserThread::UI,
                           FROM_HERE,
                           base::Bind(&StartMonitoringHelper,
                                      render_process_id,
@@ skipping 62 matching lines @@
         FROM_HERE, base::TimeDelta::FromSeconds(1) /
                        static_cast<int>(kPowerMeasurementsPerSecond),
         base::Bind(&AudioStreamMonitor::Poll, base::Unretained(this)));
   }
 }
 
 void AudioStreamMonitor::StopMonitoringStreamOnUIThread(int render_process_id,
                                                         int stream_id) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
-  const StreamID qualified_id(render_process_id, stream_id);
-  DCHECK(poll_callbacks_.find(qualified_id) != poll_callbacks_.end());
-  poll_callbacks_.erase(qualified_id);
+  // In the event of render process death, these may have already been cleared.
+  auto it = poll_callbacks_.find(StreamID(render_process_id, stream_id));
+  if (it == poll_callbacks_.end())
+    return;
 
+  poll_callbacks_.erase(it);
   if (poll_callbacks_.empty())
     poll_timer_.Stop();
 }
 
 void AudioStreamMonitor::Poll() {
   bool was_audible = is_audible_;
   is_audible_ = false;
 
   for (StreamPollCallbackMap::const_iterator it = poll_callbacks_.begin();
        it != poll_callbacks_.end();
@@ skipping 53 matching lines @@
   DCHECK(!power_level_monitoring_available());
   DCHECK_GT(active_streams_, 0u);
   if (--active_streams_ == 0u) {
     is_audible_ = false;
     web_contents_->OnAudioStateChanged(false);
     MaybeToggle();
   }
 }
 
 }  // namespace content