Refactoring the way begin frame sources inside scheduler work.

cc/output/begin_frame_args.h

Index: cc/output/begin_frame_args.h
diff --git a/cc/output/begin_frame_args.h b/cc/output/begin_frame_args.h
index b23a81e183a2180a90684cf92736d59ba3ba5804..c35a5005695faa802e0737e5bc2ba8b9661dd742 100644
--- a/cc/output/begin_frame_args.h
+++ b/cc/output/begin_frame_args.h
@@ -20,6 +20,13 @@ class TracedValue;
 namespace cc {
 
 struct CC_EXPORT BeginFrameArgs {
+  enum BeginFrameArgsType {
+    INVALID,
+    NORMAL,
+    SYNCHRONOUS,
+    MISSED,
+  };
+
   // Creates an invalid set of values.
   BeginFrameArgs();
 
@@ -28,6 +35,10 @@ struct CC_EXPORT BeginFrameArgs {
   static BeginFrameArgs Create(base::TimeTicks frame_time,
                                base::TimeTicks deadline,
                                base::TimeDelta interval);
+  static BeginFrameArgs CreateTyped(base::TimeTicks frame_time,
+                                    base::TimeTicks deadline,
+                                    base::TimeDelta interval,
+                                    BeginFrameArgsType type);
   static BeginFrameArgs CreateForSynchronousCompositor(
       base::TimeTicks now = base::TimeTicks());
 
@@ -53,11 +64,13 @@ struct CC_EXPORT BeginFrameArgs {
   base::TimeTicks frame_time;
   base::TimeTicks deadline;
   base::TimeDelta interval;
+  BeginFrameArgsType type;
 
  private:
   BeginFrameArgs(base::TimeTicks frame_time,
                  base::TimeTicks deadline,
-                 base::TimeDelta interval);
+                 base::TimeDelta interval,
+                 BeginFrameArgsType type);
 };
 
 }  // namespace cc