Adding flow traces for blink scheduler events

Source/platform/scheduler/Scheduler.h

Index: Source/platform/scheduler/Scheduler.h
diff --git a/Source/platform/scheduler/Scheduler.h b/Source/platform/scheduler/Scheduler.h
index 2467766d4857b3f0e13684574993d0670f2a8e3a..e9afcee99be231cbf79fb8b84decb52311d4bf85 100644
--- a/Source/platform/scheduler/Scheduler.h
+++ b/Source/platform/scheduler/Scheduler.h
@@ -18,6 +18,8 @@ class WebThread;
 
 namespace blink {
 
+typedef long long unsigned FlowTraceID;

[Sami, 2014/08/20 14:20:57]

Probably better to use int64_t for this. Actually, it would also be simpler just
to use a naked int64_t since that's what the rest of chromium does.

[picksi1, 2014/08/29 14:11:28]

Changed to an int so keep atomicincrement happy

+
 // The scheduler is an opinionated gateway for arranging work to be run on the
 // main thread. It decides which tasks get priority over others based on a
 // scheduling policy and the overall system state.
@@ -37,6 +39,7 @@ public:
     void postInputTask(const TraceLocation&, const Task&);
     void postCompositorTask(const TraceLocation&, const Task&);
     void postTask(const TraceLocation&, const Task&); // For generic (low priority) tasks.
+
     void postIdleTask(const TraceLocation&, const IdleTask&); // For non-critical tasks which may be reordered relative to other task types.
 
     // Returns true if there is high priority work pending on the main thread
@@ -60,10 +63,10 @@ private:
     ~Scheduler();
 
     void scheduleIdleTask(const TraceLocation&, const IdleTask&);
-
     static void sharedTimerAdapter();
     void tickSharedTimer();
 
+
     bool hasPendingHighPriorityWork() const;
     void runHighPriorityTasks();
 
@@ -71,15 +74,27 @@ private:
 
     class TracedTask {
     public:
-        TracedTask(const Task& task, const TraceLocation& location)
-            : m_task(task)
-            , m_location(location) { }
+
+        enum Type {
+            Compositor,
+            Input,
+            MainThread,
+            TypeCount
+        };
+
+        TracedTask(const Task&, const TraceLocation&, Type);
+        static void setTypeName(Type, char const*);
 
         void run();
 
+        FlowTraceID m_FlowTraceID;

[Sami, 2014/08/20 14:20:57]

s/m_FlowTraceID/m_flowTraceID/

[picksi1, 2014/08/29 14:11:28]

This is no longer static in latest version

+
     private:
         Task m_task;
         TraceLocation m_location;
+        Type m_type;

[Sami, 2014/08/20 14:20:57]

Instead of having a type enum, could we just pass the trace name as pointer to
this class? The string being pointed to is immutable so there are no lifetime
issues. This way we don't need to set up the pointers at construction time
either.

[picksi1, 2014/08/29 14:11:28]

Done.

+        static FlowTraceID s_NextFlowTraceID;
+        static char const* s_typeNames[Type::TypeCount];
     };
 
     // Should only be accessed from the main thread.