Fix Timeline reporting crash when reusing timeline events with preserialized json

runtime/vm/timeline.cc

 // 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.
 
 #include <cstdlib>
 
 #include "vm/atomic.h"
 #include "vm/isolate.h"
 #include "vm/json_stream.h"
 #include "vm/lockers.h"
@@ skipping 172 matching lines @@
       isolate_id_(ILLEGAL_PORT) {
 }
 
 
 TimelineEvent::~TimelineEvent() {
   Reset();
 }
 
 
 void TimelineEvent::Reset() {
-  set_event_type(kNone);
+  state_ = 0;
   thread_ = OSThread::kInvalidThreadId;
   isolate_id_ = ILLEGAL_PORT;
   category_ = "";
   label_ = NULL;
   FreeArguments();
+  set_pre_serialized_json(false);
+  set_event_type(kNone);
 }
 
 
 void TimelineEvent::AsyncBegin(const char* label,
                                int64_t async_id,
                                int64_t micros) {
   Init(kAsyncBegin, label);
   set_timestamp0(micros);
   // Overload timestamp1_ with the async_id.
   set_timestamp1(async_id);
@@ skipping 151 matching lines @@
     category_ = stream->name();
   } else {
     category_ = "";
   }
 }
 
 
 void TimelineEvent::Init(EventType event_type,
                          const char* label) {
   ASSERT(label != NULL);
-  set_event_type(event_type);
+  state_ = 0;
   timestamp0_ = 0;
   timestamp1_ = 0;
   OSThread* os_thread = OSThread::Current();
   ASSERT(os_thread != NULL);
   thread_ = os_thread->trace_id();
   Isolate* isolate = Isolate::Current();
   if (isolate != NULL) {
     isolate_id_ = isolate->main_port();
   } else {
     isolate_id_ = ILLEGAL_PORT;
   }
   label_ = label;
   FreeArguments();
+  set_pre_serialized_json(false);
+  set_event_type(event_type);
 }
 
 
 bool TimelineEvent::Within(int64_t time_origin_micros,
                            int64_t time_extent_micros) {
   if ((time_origin_micros == -1) ||
       (time_extent_micros == -1)) {
     // No time range specified.
     return true;
   }
@@ skipping 924 matching lines @@
 
 
 TimelineEventBlock* TimelineEventBlockIterator::Next() {
   ASSERT(current_ != NULL);
   TimelineEventBlock* r = current_;
   current_ = current_->next();
   return r;
 }
 
 }  // namespace dart