Add a timeline recorder that drops new events after its buffer is full.

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 "include/dart_tools_api.h"
 
 #include "vm/allocation.h"
@@ skipping 312 matching lines @@
   intptr_t arguments_length_;
   uword state_;
   const char* label_;
   const char* category_;
   ThreadId thread_;
   Dart_Port isolate_id_;
 
   friend class TimelineEventRecorder;
   friend class TimelineEventEndlessRecorder;
   friend class TimelineEventRingRecorder;
+  friend class TimelineEventStartupRecorder;
   friend class TimelineStream;
   friend class TimelineTestHelper;
   DISALLOW_COPY_AND_ASSIGN(TimelineEvent);
 };
 
 
 // A stream of timeline events. A stream has a name and can be enabled or
 // disabled (globally and per isolate).
 class TimelineStream {
  public:
@@ skipping 224 matching lines @@
 
   // Only accessed under the recorder's lock.
   ThreadId thread_id_;
   bool in_use_;
 
   void Open();
   void Finish();
 
   friend class Thread;
   friend class TimelineEventRecorder;
+  friend class TimelineEventEndlessRecorder;
   friend class TimelineEventRingRecorder;
-  friend class TimelineEventEndlessRecorder;
+  friend class TimelineEventStartupRecorder;
   friend class TimelineTestHelper;
   friend class JSONStream;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TimelineEventBlock);
 };
 
 
 class TimelineEventFilter : public ValueObject {
  public:
@@ skipping 93 matching lines @@
   friend class TimelineEventBlockIterator;
   friend class TimelineStream;
   friend class TimelineTestHelper;
   friend class Timeline;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TimelineEventRecorder);
 };
 
 
-// A recorder that stores events in a ring buffer of fixed capacity.
-class TimelineEventRingRecorder : public TimelineEventRecorder {
+// An abstract recorder that stores events in a buffer of fixed capacity.
+class TimelineEventFixedBufferRecorder : public TimelineEventRecorder {
  public:
   static const intptr_t kDefaultCapacity = 8192;
 
-  explicit TimelineEventRingRecorder(intptr_t capacity = kDefaultCapacity);
-  ~TimelineEventRingRecorder();
+  explicit TimelineEventFixedBufferRecorder(intptr_t capacity);
+  ~TimelineEventFixedBufferRecorder();
 
   void PrintJSON(JSONStream* js, TimelineEventFilter* filter);
   void PrintTraceEvent(JSONStream* js, TimelineEventFilter* filter);
-  const char* name() const {
-    return "ring";
-  }
 
  protected:
   TimelineEvent* StartEvent();
   void CompleteEvent(TimelineEvent* event);
   TimelineEventBlock* GetHeadBlockLocked();
   intptr_t FindOldestBlockIndex() const;
-  TimelineEventBlock* GetNewBlockLocked();
   void Clear();
 
   void PrintJSONEvents(JSONArray* array, TimelineEventFilter* filter);
 
   TimelineEventBlock** blocks_;
   intptr_t capacity_;
   intptr_t num_blocks_;
   intptr_t block_cursor_;
 };
 
 
+// A recorder that stores events in a buffer of fixed capacity. When the buffer
+// is full, new events overwrite old events.
+class TimelineEventRingRecorder : public TimelineEventFixedBufferRecorder {
+ public:
+  explicit TimelineEventRingRecorder(intptr_t capacity = kDefaultCapacity)
+      : TimelineEventFixedBufferRecorder(capacity) {}
+  ~TimelineEventRingRecorder() {}
+
+  const char* name() const {
+    return "ring";
+  }
+
+ protected:
+  TimelineEventBlock* GetNewBlockLocked();
+};
+
+
+// A recorder that stores events in a buffer of fixed capacity. When the buffer
+// is full, new events are dropped.
+class TimelineEventStartupRecorder : public TimelineEventFixedBufferRecorder {
+ public:
+  explicit TimelineEventStartupRecorder(intptr_t capacity = kDefaultCapacity)
+      : TimelineEventFixedBufferRecorder(capacity) {}
+  ~TimelineEventStartupRecorder() {}
+
+  const char* name() const {
+    return "startup";
+  }
+
+ protected:
+  TimelineEventBlock* GetNewBlockLocked();
+};
+
+
 // An abstract recorder that calls |OnEvent| whenever an event is complete.
 // This should only be used for testing.
 class TimelineEventCallbackRecorder : public TimelineEventRecorder {
  public:
   TimelineEventCallbackRecorder();
   ~TimelineEventCallbackRecorder();
 
   void PrintJSON(JSONStream* js, TimelineEventFilter* filter);
   void PrintTraceEvent(JSONStream* js, TimelineEventFilter* filter);
 
@@ skipping 65 matching lines @@
 
  private:
   TimelineEventBlock* current_;
   TimelineEventRecorder* recorder_;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_TIMELINE_H_