[vm] Support flow events in Dart_TimelineEvent.

runtime/vm/timeline.h

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_TIMELINE_H_
 #define RUNTIME_VM_TIMELINE_H_
 
 #include "include/dart_tools_api.h"
 
 #include "vm/allocation.h"
@@ skipping 140 matching lines @@
   enum EventType {
     kNone,
     kBegin,
     kEnd,
     kDuration,
     kInstant,
     kAsyncBegin,
     kAsyncInstant,
     kAsyncEnd,
     kCounter,
+    kFlowBegin,
+    kFlowStep,
+    kFlowEnd,
     kMetadata,
     kNumEventTypes,
   };
 
   TimelineEvent();
   ~TimelineEvent();
 
   void Reset();
 
   bool IsValid() const {
@@ skipping 32 matching lines @@
              int64_t micros = OS::GetCurrentMonotonicMicros(),
              int64_t thread_micros = OS::GetCurrentThreadCPUMicros());
 
   void End(const char* label,
            int64_t micros = OS::GetCurrentMonotonicMicros(),
            int64_t thread_micros = OS::GetCurrentThreadCPUMicros());
 
   void Counter(const char* label,
                int64_t micros = OS::GetCurrentMonotonicMicros());
 
+  void FlowBegin(const char* label,
+                 int64_t async_id,
+                 int64_t micros = OS::GetCurrentMonotonicMicros());
+  void FlowStep(const char* label,
+                int64_t async_id,
+                int64_t micros = OS::GetCurrentMonotonicMicros());
+  void FlowEnd(const char* label,
+               int64_t async_id,
+               int64_t micros = OS::GetCurrentMonotonicMicros());
+
   void Metadata(const char* label,
                 int64_t micros = OS::GetCurrentMonotonicMicros());
 
   // Completes this event with pre-serialized JSON. Copies |json|.
   void CompleteWithPreSerializedJSON(const char* json);
 
   // Set the number of arguments in the event.
   void SetNumArguments(intptr_t length);
   // |name| must be a compile time constant. Takes ownership of |argument|.
   void SetArgument(intptr_t i, const char* name, char* argument);
@@ skipping 626 matching lines @@
 
  private:
   TimelineEventBlock* current_;
   TimelineEventRecorder* recorder_;
 };
 
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_TIMELINE_H_