Bug 1070216 - Properly manage lifetime of allocated CaptureDevices. r=jib

We currently avoid Deallocating a CaptureDevice used for multiple gUMStreams
when one of them calls Deallocate() by keeping track of how many called
Start().

The normal lifetime sequence however, is:
Allocate()
Start()
Stop()
Deallocate()

This patches fixes the lifetime management by keeping track of how many
users of the CaptureDevice called Allocate().

--HG--
extra : commitid : J9Hj3Lffpg
extra : rebase_source : 0f9928a45c4810b3d6236bdf8a71587ad46de601

dom/media/webrtc/MediaEngineCameraVideoSource.h

@@ -28,6 +28,7 @@ public:
     , mHeight(0)
     , mInitDone(false)
     , mHasDirectListeners(false)
+    , mNrAllocations(0)
     , mCaptureIndex(aIndex)
     , mTrackID(0)
   {}
@@ -115,6 +116,7 @@ static void LogCapability(const char* aHeader,
 
   bool mInitDone;
   bool mHasDirectListeners;
+  int mNrAllocations; // When this becomes 0, we shut down HW
   int mCaptureIndex;
   TrackID mTrackID;
 

dom/media/webrtc/MediaEngineRemoteVideoSource.cpp

@@ -97,7 +97,12 @@ MediaEngineRemoteVideoSource::Allocate(const dom::MediaTrackConstraints& aConstr
 {
   LOG((__PRETTY_FUNCTION__));
 
-  if (mState == kReleased && mInitDone) {
+  if (!mInitDone) {
+    LOG(("Init not done"));
+    return NS_ERROR_FAILURE;
+  }
+
+  if (mState == kReleased) {
     // Note: if shared, we don't allow a later opener to affect the resolution.
     // (This may change depending on spec changes for Constraints/settings)
 
@@ -121,19 +126,20 @@ MediaEngineRemoteVideoSource::Allocate(const dom::MediaTrackConstraints& aConstr
     }
   }
 
+  ++mNrAllocations;
+
   return NS_OK;
 }
 
 nsresult
 MediaEngineRemoteVideoSource::Deallocate()
 {
-  LOG((__FUNCTION__));
-  bool empty;
-  {
-    MonitorAutoLock lock(mMonitor);
-    empty = mSources.IsEmpty();
-  }
-  if (empty) {
+  LOG((__PRETTY_FUNCTION__));
+
+  --mNrAllocations;
+  MOZ_ASSERT(mNrAllocations >= 0, "Double-deallocations are prohibited");
+
+  if (mNrAllocations == 0) {
     if (mState != kStopped && mState != kAllocated) {
       return NS_ERROR_FAILURE;
     }

dom/media/webrtc/MediaEngineWebRTC.h

@@ -135,6 +135,7 @@ public:
     , mThread(aThread)
     , mCapIndex(aIndex)
     , mChannel(-1)
+    , mNrAllocations(0)
     , mInitDone(false)
     , mStarted(false)
     , mSampleFrequency(MediaEngine::DEFAULT_SAMPLE_RATE)
@@ -215,10 +216,11 @@ private:
   // from kStarted to kStopped (which are combined with EndTrack()).
   // mSources[] is accessed from webrtc threads.
   Monitor mMonitor;
-  nsTArray<nsRefPtr<SourceMediaStream>> mSources; // When this goes empty, we shut down HW
+  nsTArray<nsRefPtr<SourceMediaStream>> mSources;
   nsCOMPtr<nsIThread> mThread;
   int mCapIndex;
   int mChannel;
+  int mNrAllocations; // When this becomes 0, we shut down HW
   TrackID mTrackID;
   bool mInitDone;
   bool mStarted;

dom/media/webrtc/MediaEngineWebRTCAudio.cpp

@@ -305,18 +305,16 @@ MediaEngineWebRTCMicrophoneSource::Allocate(const dom::MediaTrackConstraints &aC
       LOG(("Audio device %d allocated shared", mCapIndex));
     }
   }
+  ++mNrAllocations;
   return NS_OK;
 }
 
 nsresult
 MediaEngineWebRTCMicrophoneSource::Deallocate()
 {
-  bool empty;
-  {
-    MonitorAutoLock lock(mMonitor);
-    empty = mSources.IsEmpty();
-  }
-  if (empty) {
+  --mNrAllocations;
+  MOZ_ASSERT(mNrAllocations >= 0, "Double-deallocations are prohibited");
+  if (mNrAllocations == 0) {
     // If empty, no callbacks to deliver data should be occuring
     if (mState != kStopped && mState != kAllocated) {
       return NS_ERROR_FAILURE;