Add TimelineBeginEndScope helper class

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 VM_TIMELINE_H_
 #define VM_TIMELINE_H_
 
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
 #include "vm/os.h"
@@ skipping 316 matching lines @@
                             "Compile" suffix);                                 \
   if (tds.enabled()) {                                                         \
     tds.SetNumArguments(1);                                                    \
     tds.CopyArgument(                                                          \
         0,                                                                     \
         "function",                                                            \
         const_cast<char*>(function.ToLibNamePrefixedQualifiedCString()));      \
   }
 
 
-class TimelineDurationScope : public StackResource {
+// See |TimelineDurationScope| and |TimelineBeginEndScope|.
+class TimelineEventScope : public StackResource {
  public:
-  TimelineDurationScope(TimelineStream* stream,
-                        const char* label);
-
-  TimelineDurationScope(Thread* thread,
-                        TimelineStream* stream,
-                        const char* label);
-
-  ~TimelineDurationScope();
-
   bool enabled() const {
     return enabled_;
   }
 
   void SetNumArguments(intptr_t length);
 
   void SetArgument(intptr_t i, const char* name, char* argument);
 
   void CopyArgument(intptr_t i, const char* name, const char* argument);
 
   void FormatArgument(intptr_t i,
                       const char* name,
                       const char* fmt, ...)  PRINTF_ATTRIBUTE(4, 5);
 
+ protected:
+  TimelineEventScope(TimelineStream* stream,
+                     const char* label);
+
+  TimelineEventScope(Thread* thread,
+                     TimelineStream* stream,
+                     const char* label);
+
+  bool ShouldEmitEvent() const {
+    return enabled_;
+  }
+
+  const char* label() const {
+    return label_;
+  }
+
+  TimelineStream* stream() const {
+    return stream_;
+  }
+
+  virtual ~TimelineEventScope();
+
+  void StealArguments(TimelineEvent* event);
+
  private:
   void Init();
   void FreeArguments();
 
-  int64_t timestamp_;
   TimelineStream* stream_;
   const char* label_;
   TimelineEventArgument* arguments_;
   intptr_t arguments_length_;
   bool enabled_;
 
+  DISALLOW_COPY_AND_ASSIGN(TimelineEventScope);
+};
+
+
+class TimelineDurationScope : public TimelineEventScope {
+ public:
+  TimelineDurationScope(TimelineStream* stream,
+                        const char* label);
+
+  TimelineDurationScope(Thread* thread,
+                        TimelineStream* stream,
+                        const char* label);
+
+  ~TimelineDurationScope();
+
+ private:
+  int64_t timestamp_;
+
   DISALLOW_COPY_AND_ASSIGN(TimelineDurationScope);
 };
 
 
+class TimelineBeginEndScope : public TimelineEventScope {
+ public:
+  TimelineBeginEndScope(TimelineStream* stream,
+                        const char* label);
+
+  TimelineBeginEndScope(Thread* thread,
+                        TimelineStream* stream,
+                        const char* label);
+
+  ~TimelineBeginEndScope();
+
+ private:
+  void EmitBegin();
+  void EmitEnd();
+
+  DISALLOW_COPY_AND_ASSIGN(TimelineBeginEndScope);
+};
+
+
 // A block of |TimelineEvent|s. Not thread safe.
 class TimelineEventBlock {
  public:
   static const intptr_t kBlockSize = 64;
 
   explicit TimelineEventBlock(intptr_t index);
   ~TimelineEventBlock();
 
   TimelineEventBlock* next() const {
     return next_;
@@ skipping 266 matching lines @@
 
  private:
   TimelineEventBlock* current_;
   TimelineEventRecorder* recorder_;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_TIMELINE_H_