Allocate the fixed-size timeline buffer with virtual memory instead of malloc.

runtime/vm/timeline_macos.cc

 // Copyright (c) 2017, 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.
 
 #include "platform/globals.h"
 #if defined(HOST_OS_MACOS) && !defined(PRODUCT)
 
 #include "vm/timeline.h"
 
 namespace dart {
@@ skipping 15 matching lines @@
 const char* TimelineEventPlatformRecorder::name() const {
   return "Systrace";
 }
 
 TimelineEventBlock* TimelineEventPlatformRecorder::GetNewBlockLocked() {
   // TODO(johnmccutchan): This function should only hand out blocks
   // which have been marked as finished.
   if (block_cursor_ == num_blocks_) {
     block_cursor_ = 0;
   }
-  TimelineEventBlock* block = blocks_[block_cursor_++];
+  TimelineEventBlock* block = &blocks_[block_cursor_++];
   block->Reset();
   block->Open();
   return block;
 }
 
 void TimelineEventPlatformRecorder::CompleteEvent(TimelineEvent* event) {
   if (event == NULL) {
     return;
   }
   ThreadBlockCompleteEvent(event);
@@ skipping 31 matching lines @@
                                                   const char* category,
                                                   const char* name,
                                                   const char* args) {
   DartCommonTimelineEventHelpers::ReportInstantEvent(thread, zone, event, start,
                                                      category, name, args);
 }
 
 }  // namespace dart
 
 #endif  // defined(HOST_OS_MACOS) && !defined(PRODUCT)