Refactor external begin frame source into a base class

content/renderer/gpu/compositor_external_begin_frame_source.cc

Index: content/renderer/gpu/compositor_external_begin_frame_source.cc
diff --git a/content/renderer/gpu/compositor_external_begin_frame_source.cc b/content/renderer/gpu/compositor_external_begin_frame_source.cc
index e2d13608ac781ece2ba7576d23a3ef8cade0cfb6..0538f47bdb989da90b4d67de9dfaedb65816a859 100644
--- a/content/renderer/gpu/compositor_external_begin_frame_source.cc
+++ b/content/renderer/gpu/compositor_external_begin_frame_source.cc
@@ -14,17 +14,18 @@ CompositorExternalBeginFrameSource::CompositorExternalBeginFrameSource(
     CompositorForwardingMessageFilter* filter,
     IPC::SyncMessageFilter* sync_message_filter,
     int routing_id)
-    : begin_frame_source_filter_(filter),
+    : external_begin_frame_source_(this),
+      begin_frame_source_filter_(filter),
       message_sender_(sync_message_filter),
       routing_id_(routing_id) {
-  DCHECK(begin_frame_source_filter_.get());
-  DCHECK(message_sender_.get());
+  DCHECK(begin_frame_source_filter_);
+  DCHECK(message_sender_);
   DetachFromThread();
 }
 
 CompositorExternalBeginFrameSource::~CompositorExternalBeginFrameSource() {
   DCHECK(CalledOnValidThread());
-  if (begin_frame_source_proxy_.get()) {
+  if (begin_frame_source_proxy_) {
     begin_frame_source_proxy_->ClearBeginFrameSource();
     begin_frame_source_filter_->RemoveHandlerOnCompositorThread(
                                     routing_id_,
@@ -35,56 +36,34 @@ CompositorExternalBeginFrameSource::~CompositorExternalBeginFrameSource() {
 void CompositorExternalBeginFrameSource::AddObserver(
     cc::BeginFrameObserver* obs) {
   DCHECK(CalledOnValidThread());
-  DCHECK(obs);
-  DCHECK(observers_.find(obs) == observers_.end());
 
-  SetClientReady();
-  bool observers_was_empty = observers_.empty();
-  observers_.insert(obs);
-  obs->OnBeginFrameSourcePausedChanged(paused_);
-  if (observers_was_empty)
-    Send(new ViewHostMsg_SetNeedsBeginFrames(routing_id_, true));
-
-  // Send a MISSED begin frame if necessary.
-  if (missed_begin_frame_args_.IsValid()) {
-    cc::BeginFrameArgs last_args = obs->LastUsedBeginFrameArgs();
-    if (!last_args.IsValid() ||
-        (missed_begin_frame_args_.frame_time > last_args.frame_time)) {
-      obs->OnBeginFrame(missed_begin_frame_args_);
-    }
+  if (!begin_frame_source_proxy_) {
+    begin_frame_source_proxy_ =
+        new CompositorExternalBeginFrameSourceProxy(this);
+    begin_frame_source_filter_handler_ =
+        base::Bind(&CompositorExternalBeginFrameSourceProxy::OnMessageReceived,
+                   begin_frame_source_proxy_);
+    begin_frame_source_filter_->AddHandlerOnCompositorThread(
+        routing_id_, begin_frame_source_filter_handler_);
   }
+
+  external_begin_frame_source_.AddObserver(obs);
 }
 
 void CompositorExternalBeginFrameSource::RemoveObserver(
     cc::BeginFrameObserver* obs) {
-  DCHECK(obs);
-  DCHECK(observers_.find(obs) != observers_.end());
-
-  observers_.erase(obs);
-  if (observers_.empty()) {
-    missed_begin_frame_args_ = cc::BeginFrameArgs();
-    Send(new ViewHostMsg_SetNeedsBeginFrames(routing_id_, false));
-  }
+  external_begin_frame_source_.RemoveObserver(obs);
 }
 
-void CompositorExternalBeginFrameSource::SetClientReady() {
-  DCHECK(CalledOnValidThread());
-  if (begin_frame_source_proxy_)
-    return;
-  begin_frame_source_proxy_ =
-      new CompositorExternalBeginFrameSourceProxy(this);
-  begin_frame_source_filter_handler_ = base::Bind(
-      &CompositorExternalBeginFrameSourceProxy::OnMessageReceived,
-      begin_frame_source_proxy_);
-  begin_frame_source_filter_->AddHandlerOnCompositorThread(
-      routing_id_,
-      begin_frame_source_filter_handler_);
+void CompositorExternalBeginFrameSource::OnNeedsBeginFrames(
+    bool needs_begin_frames) {
+  Send(new ViewHostMsg_SetNeedsBeginFrames(routing_id_, needs_begin_frames));
 }
 
 void CompositorExternalBeginFrameSource::OnMessageReceived(
     const IPC::Message& message) {
   DCHECK(CalledOnValidThread());
-  DCHECK(begin_frame_source_proxy_.get());
+  DCHECK(begin_frame_source_proxy_);
   IPC_BEGIN_MESSAGE_MAP(CompositorExternalBeginFrameSource, message)
     IPC_MESSAGE_HANDLER(ViewMsg_SetBeginFramePaused,
                         OnSetBeginFrameSourcePaused)
@@ -94,22 +73,12 @@ void CompositorExternalBeginFrameSource::OnMessageReceived(
 
 void CompositorExternalBeginFrameSource::OnSetBeginFrameSourcePaused(
     bool paused) {
-  if (paused_ == paused)
-    return;
-  paused_ = paused;
-  std::unordered_set<cc::BeginFrameObserver*> observers(observers_);
-  for (auto* obs : observers)
-    obs->OnBeginFrameSourcePausedChanged(paused_);
+  external_begin_frame_source_.OnSetBeginFrameSourcePaused(paused);
 }
 
 void CompositorExternalBeginFrameSource::OnBeginFrame(
-  const cc::BeginFrameArgs& args) {
-  DCHECK(CalledOnValidThread());
-  missed_begin_frame_args_ = args;
-  missed_begin_frame_args_.type = cc::BeginFrameArgs::MISSED;
-  std::unordered_set<cc::BeginFrameObserver*> observers(observers_);
-  for (auto* obs : observers)
-    obs->OnBeginFrame(args);
+    const cc::BeginFrameArgs& args) {
+  external_begin_frame_source_.OnBeginFrame(args);
 }
 
 bool CompositorExternalBeginFrameSource::Send(IPC::Message* message) {