Adds BeginFrameControl via DevTools.

cc/output/begin_frame_args.cc

Index: cc/output/begin_frame_args.cc
diff --git a/cc/output/begin_frame_args.cc b/cc/output/begin_frame_args.cc
index 7ef2c4842ac4b30610a7acd9dd416f5f5270fc8a..76d1509a28ead13d37e5cdf11f73873a8f1ed1e9 100644
--- a/cc/output/begin_frame_args.cc
+++ b/cc/output/begin_frame_args.cc
@@ -29,8 +29,8 @@ BeginFrameArgs::BeginFrameArgs()
       deadline(base::TimeTicks()),
       interval(base::TimeDelta::FromMicroseconds(-1)),
       type(BeginFrameArgs::INVALID),
-      on_critical_path(true) {
-}
+      on_critical_path(true),
+      allow_latency_optimizations(true) {}
 
 BeginFrameArgs::BeginFrameArgs(base::TimeTicks frame_time,
                                base::TimeTicks deadline,
@@ -40,8 +40,8 @@ BeginFrameArgs::BeginFrameArgs(base::TimeTicks frame_time,
       deadline(deadline),
       interval(interval),
       type(type),
-      on_critical_path(true) {
-}
+      on_critical_path(true),
+      allow_latency_optimizations(true) {}
 
 BeginFrameArgs BeginFrameArgs::Create(BeginFrameArgs::CreationLocation location,
                                       base::TimeTicks frame_time,
@@ -77,6 +77,7 @@ void BeginFrameArgs::AsValueInto(base::trace_event::TracedValue* state) const {
   state->SetString("created_from", created_from.ToString());
 #endif
   state->SetBoolean("on_critical_path", on_critical_path);
+  state->SetBoolean("allow_latency_optimizations", allow_latency_optimizations);
 }
 
 // This is a hard-coded deadline adjustment that assumes 60Hz, to be used in