Revert of https://crrev.com/290125, causing browser crashes due to race

TBR=vrk@chromium.org
BUG=404767
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/503183002

Cr-Commit-Position: refs/heads/master@{#291798}

content/browser/renderer_host/media/peer_connection_tracker_host.cc

@@ -3,20 +3,14 @@
 // found in the LICENSE file.
 #include "content/browser/renderer_host/media/peer_connection_tracker_host.h"
 
-#include "base/power_monitor/power_monitor.h"
 #include "content/browser/media/webrtc_internals.h"
 #include "content/common/media/peer_connection_tracker_messages.h"
-#include "content/public/browser/render_process_host.h"
 
 namespace content {
 
 PeerConnectionTrackerHost::PeerConnectionTrackerHost(int render_process_id)
     : BrowserMessageFilter(PeerConnectionTrackerMsgStart),
-      render_process_id_(render_process_id) {
-  base::PowerMonitor* power_monitor = base::PowerMonitor::Get();
-  if (power_monitor)
-    power_monitor->AddObserver(this);
-}
+      render_process_id_(render_process_id) {}
 
 bool PeerConnectionTrackerHost::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
@@ -42,9 +36,6 @@ void PeerConnectionTrackerHost::OverrideThreadForMessage(
 }
 
 PeerConnectionTrackerHost::~PeerConnectionTrackerHost() {
-  base::PowerMonitor* power_monitor = base::PowerMonitor::Get();
-  if (power_monitor)
-    power_monitor->RemoveObserver(this);
 }
 
 void PeerConnectionTrackerHost::OnAddPeerConnection(
@@ -91,11 +82,4 @@ void PeerConnectionTrackerHost::OnGetUserMedia(
                                                  video_constraints);
 }
 
-void PeerConnectionTrackerHost::OnSuspend() {
-  content::RenderProcessHost* host =
-      content::RenderProcessHost::FromID(render_process_id_);
-  if (host)
-    host->Send(new PeerConnectionTracker_OnSuspend());
-}
-
 }  // namespace content

content/browser/renderer_host/media/peer_connection_tracker_host.h

@@ -5,7 +5,6 @@
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_PEER_CONNECTION_TRACKER_HOST_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_PEER_CONNECTION_TRACKER_HOST_H_
 
-#include "base/power_monitor/power_observer.h"
 #include "content/public/browser/browser_message_filter.h"
 
 struct PeerConnectionInfo;
@@ -17,11 +16,9 @@ class ListValue;
 namespace content {
 
 // This class is the host for PeerConnectionTracker in the browser process
-// managed by RenderProcessHostImpl. It receives PeerConnection events from
-// PeerConnectionTracker as IPC messages that it forwards to WebRTCInternals.
-// It also forwards browser process events to PeerConnectionTracker via IPC.
-class PeerConnectionTrackerHost : public BrowserMessageFilter,
-                                  public base::PowerObserver {
+// managed by RenderProcessHostImpl. It passes IPC messages between
+// WebRTCInternals and PeerConnectionTracker.
+class PeerConnectionTrackerHost : public BrowserMessageFilter {
  public:
   PeerConnectionTrackerHost(int render_process_id);
 
@@ -30,9 +27,6 @@ class PeerConnectionTrackerHost : public BrowserMessageFilter,
   virtual void OverrideThreadForMessage(const IPC::Message& message,
                                         BrowserThread::ID* thread) OVERRIDE;
 
-  // base::PowerObserver override.
-  virtual void OnSuspend() OVERRIDE;
-
  protected:
   virtual ~PeerConnectionTrackerHost();
 

content/common/media/peer_connection_tracker_messages.h

@@ -40,4 +40,3 @@ IPC_MESSAGE_CONTROL5(PeerConnectionTrackerHost_GetUserMedia,
 
 // Messages sent to PeerConnectionTracker.
 IPC_MESSAGE_CONTROL0(PeerConnectionTracker_GetAllStats)
-IPC_MESSAGE_CONTROL0(PeerConnectionTracker_OnSuspend)

content/renderer/media/peer_connection_tracker.cc

@@ -278,7 +278,6 @@ bool PeerConnectionTracker::OnControlMessageReceived(
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(PeerConnectionTracker, message)
     IPC_MESSAGE_HANDLER(PeerConnectionTracker_GetAllStats, OnGetAllStats)
-    IPC_MESSAGE_HANDLER(PeerConnectionTracker_OnSuspend, OnSuspend)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
@@ -298,13 +297,6 @@ void PeerConnectionTracker::OnGetAllStats() {
   }
 }
 
-void PeerConnectionTracker::OnSuspend() {
-  for (PeerConnectionIdMap::iterator it = peer_connection_id_map_.begin();
-       it != peer_connection_id_map_.end(); ++it) {
-    it->first->stop();
-  }
-}
-
 void PeerConnectionTracker::RegisterPeerConnection(
     RTCPeerConnectionHandler* pc_handler,
     const webrtc::PeerConnectionInterface::RTCConfiguration& config,

content/renderer/media/peer_connection_tracker.h

@@ -161,9 +161,6 @@ class CONTENT_EXPORT PeerConnectionTracker : public RenderProcessObserver {
   // IPC Message handler for getting all stats.
   void OnGetAllStats();
 
-  // Called when the browser process reports a suspend event from the OS.
-  void OnSuspend();
-
   void SendPeerConnectionUpdate(RTCPeerConnectionHandler* pc_handler,
                                 const std::string& callback_type,
                                 const std::string& value);