cc: Making BeginFrameSources support multiple BeginFrameObservers.

cc/scheduler/begin_frame_source.cc

Index: cc/scheduler/begin_frame_source.cc
diff --git a/cc/scheduler/begin_frame_source.cc b/cc/scheduler/begin_frame_source.cc
index 42b8f6f1c735db05dfca52c00ed6070bb8b63a36..8eb0155bee7ab05307103c04c439d9a3a54e509b 100644
--- a/cc/scheduler/begin_frame_source.cc
+++ b/cc/scheduler/begin_frame_source.cc
@@ -33,7 +33,7 @@ BeginFrameObserverMixIn::BeginFrameObserverMixIn()
     : last_begin_frame_args_(), dropped_begin_frame_args_(0) {
 }
 
-const BeginFrameArgs BeginFrameObserverMixIn::LastUsedBeginFrameArgs() const {
+const BeginFrameArgs BeginFrameObserverMixIn::LastUsedBeginFrameArgs() {
   return last_begin_frame_args_;
 }
 void BeginFrameObserverMixIn::OnBeginFrame(const BeginFrameArgs& args) {
@@ -53,7 +53,7 @@ void BeginFrameObserverMixIn::OnBeginFrame(const BeginFrameArgs& args) {
 }
 
 void BeginFrameObserverMixIn::AsValueInto(
-    base::trace_event::TracedValue* dict) const {
+    base::trace_event::TracedValue* dict) {
   dict->BeginDictionary("last_begin_frame_args_");
   last_begin_frame_args_.AsValueInto(dict);
   dict->EndDictionary();
@@ -62,13 +62,15 @@ void BeginFrameObserverMixIn::AsValueInto(
 
 // BeginFrameSourceMixIn ------------------------------------------------------
 BeginFrameSourceMixIn::BeginFrameSourceMixIn()
-    : observer_(NULL),
+    : observer_list_(),
       needs_begin_frames_(false),
       inside_as_value_into_(false) {
-  DCHECK(!observer_);
   DCHECK_EQ(inside_as_value_into_, false);
 }
 
+BeginFrameSourceMixIn::~BeginFrameSourceMixIn() {
+}
+
 bool BeginFrameSourceMixIn::NeedsBeginFrames() const {
   return needs_begin_frames_;
 }
@@ -86,56 +88,51 @@ void BeginFrameSourceMixIn::SetNeedsBeginFrames(bool needs_begin_frames) {
 }
 
 void BeginFrameSourceMixIn::AddObserver(BeginFrameObserver* obs) {
-  DEBUG_FRAMES("BeginFrameSourceMixIn::AddObserver",
-               "current observer",
-               observer_,
-               "to add observer",
-               obs);
-  DCHECK(!observer_);
-  observer_ = obs;
+  DEBUG_FRAMES("BeginFrameSourceMixIn::AddObserver", "has observers?",
+               (observer_list_).might_have_observers(), "to add observer", obs);
+  DCHECK(obs);
+  DCHECK(!observer_list_.HasObserver(obs));
+  observer_list_.AddObserver(obs);
 }
 
 void BeginFrameSourceMixIn::RemoveObserver(BeginFrameObserver* obs) {
-  DEBUG_FRAMES("BeginFrameSourceMixIn::RemoveObserver",
-               "current observer",
-               observer_,
-               "to remove observer",
+  DEBUG_FRAMES("BeginFrameSourceMixIn::RemoveObserver", "has observers?",
+               (observer_list_).might_have_observers(), "to remove observer",
                obs);
-  DCHECK_EQ(observer_, obs);
-  observer_ = NULL;
+  DCHECK(obs);
+  DCHECK(observer_list_.HasObserver(obs));
+  observer_list_.RemoveObserver(obs);
 }
 
 void BeginFrameSourceMixIn::CallOnBeginFrame(const BeginFrameArgs& args) {
-  DEBUG_FRAMES("BeginFrameSourceMixIn::CallOnBeginFrame",
-               "current observer",
-               observer_,
-               "args",
-               args.AsValue());
-  if (observer_) {
-    return observer_->OnBeginFrame(args);
-  }
+  DEBUG_FRAMES("BeginFrameSourceMixIn::CallOnBeginFrame", "has observers?",
+               observer_list_.might_have_observers(), "args", args.AsValue());
+  FOR_EACH_OBSERVER(BeginFrameObserver, observer_list_, OnBeginFrame(args));
 }
 
 // Tracing support
-void BeginFrameSourceMixIn::AsValueInto(
-    base::trace_event::TracedValue* dict) const {
+void BeginFrameSourceMixIn::AsValueInto(base::trace_event::TracedValue* dict) {
   // As the observer might try to trace the source, prevent an infinte loop
   // from occuring.
   if (inside_as_value_into_) {
     dict->SetString("observer", "<loop detected>");
     return;
   }
+  base::AutoReset<bool> prevent_loops(const_cast<bool*>(&inside_as_value_into_),
+                                      true);
 
-  if (observer_) {
-    base::AutoReset<bool> prevent_loops(
-        const_cast<bool*>(&inside_as_value_into_), true);
-    dict->BeginDictionary("observer");
-    observer_->AsValueInto(dict);
-    dict->EndDictionary();
-  } else {
-    dict->SetString("observer", "NULL");
-  }
   dict->SetBoolean("needs_begin_frames", NeedsBeginFrames());
+  if (observer_list_.might_have_observers()) {
+    ObserverList<BeginFrameObserver>::Iterator it(&observer_list_);
+    BeginFrameObserver* obs;
+    dict->BeginArray("observers");
+    while ((obs = it.GetNext()) != NULL) {
+      dict->BeginDictionary();
+      obs->AsValueInto(dict);
+      dict->EndDictionary();
+    }
+    dict->EndArray();
+  }
 }
 
 // BackToBackBeginFrameSourceMixIn --------------------------------------------
@@ -199,7 +196,7 @@ void BackToBackBeginFrameSource::DidFinishFrame(size_t remaining_frames) {
 
 // Tracing support
 void BackToBackBeginFrameSource::AsValueInto(
-    base::trace_event::TracedValue* dict) const {
+    base::trace_event::TracedValue* dict) {

[danakj, 2015/03/25 18:12:55]

What's with all the const changes? AsValueInto can't be related to using an
ObserverList?

[mithro-old, 2015/03/26 00:54:49]

The AsValueInto loops over each of the observers. Iterating over an ObserverList
is non const operation.

   dict->SetString("type", "BackToBackBeginFrameSource");
   BeginFrameSourceMixIn::AsValueInto(dict);
   dict->SetBoolean("send_begin_frame_posted_", send_begin_frame_posted_);
@@ -267,7 +264,7 @@ void SyntheticBeginFrameSource::OnNeedsBeginFramesChange(
 
 // Tracing support
 void SyntheticBeginFrameSource::AsValueInto(
-    base::trace_event::TracedValue* dict) const {
+    base::trace_event::TracedValue* dict) {
   dict->SetString("type", "SyntheticBeginFrameSource");
   BeginFrameSourceMixIn::AsValueInto(dict);
 
@@ -394,12 +391,19 @@ void BeginFrameSourceMultiplexer::OnBeginFrame(const BeginFrameArgs& args) {
   CallOnBeginFrame(args);
 }
 
-const BeginFrameArgs BeginFrameSourceMultiplexer::LastUsedBeginFrameArgs()
-    const {
-  if (observer_)
-    return observer_->LastUsedBeginFrameArgs();
-  else
-    return BeginFrameArgs();
+const BeginFrameArgs BeginFrameSourceMultiplexer::LastUsedBeginFrameArgs() {
+  BeginFrameArgs last;
+
+  if ((observer_list_).might_have_observers()) {
+    ObserverList<BeginFrameObserver>::Iterator it(&observer_list_);
+    BeginFrameObserver* obs;
+    while ((obs = it.GetNext()) != NULL) {
+      BeginFrameArgs obs_last = obs->LastUsedBeginFrameArgs();
+      if (obs_last.frame_time > last.frame_time)
+        last = obs_last;
+    }
+  }
+  return last;
 }
 
 // BeginFrameSource support
@@ -428,16 +432,11 @@ void BeginFrameSourceMultiplexer::DidFinishFrame(size_t remaining_frames) {
 
 // Tracing support
 void BeginFrameSourceMultiplexer::AsValueInto(
-    base::trace_event::TracedValue* dict) const {
+    base::trace_event::TracedValue* dict) {
   dict->SetString("type", "BeginFrameSourceMultiplexer");
+  BeginFrameSourceMixIn::AsValueInto(dict);
 
   dict->SetInteger("minimum_interval_us", minimum_interval_.InMicroseconds());
-  if (observer_) {
-    dict->BeginDictionary("last_begin_frame_args");
-    observer_->LastUsedBeginFrameArgs().AsValueInto(dict);
-    dict->EndDictionary();
-  }
-
   if (active_source_) {
     dict->BeginDictionary("active_source");
     active_source_->AsValueInto(dict);
@@ -464,17 +463,15 @@ bool BeginFrameSourceMultiplexer::HasSource(BeginFrameSource* source) {
 
 bool BeginFrameSourceMultiplexer::IsIncreasing(const BeginFrameArgs& args) {
   DCHECK(args.IsValid());
-  if (!observer_)
-    return false;
 
   // If the last begin frame is invalid, then any new begin frame is valid.
-  if (!observer_->LastUsedBeginFrameArgs().IsValid())
+  if (!LastUsedBeginFrameArgs().IsValid())
     return true;
 
   // Only allow new args have a *strictly bigger* frame_time value and statisfy
   // minimum interval requirement.
   return (args.frame_time >=
-          observer_->LastUsedBeginFrameArgs().frame_time + minimum_interval_);
+          LastUsedBeginFrameArgs().frame_time + minimum_interval_);
 }
 
 }  // namespace cc