[tracing] Implement Add/RemoveTraceStateObserver for default platform.

src/libplatform/default-platform.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/libplatform/default-platform.h"
 
 #include <algorithm>
 #include <queue>
 
 #include "src/base/logging.h"
@@ skipping 21 matching lines @@
 void SetTracingController(
     v8::Platform* platform,
     v8::platform::tracing::TracingController* tracing_controller) {
   return reinterpret_cast<DefaultPlatform*>(platform)->SetTracingController(
       tracing_controller);
 }
 
 const int DefaultPlatform::kMaxThreadPoolSize = 8;
 
 DefaultPlatform::DefaultPlatform()
-    : initialized_(false), thread_pool_size_(0), tracing_controller_(NULL) {}
+    : initialized_(false), thread_pool_size_(0) {}
 
 DefaultPlatform::~DefaultPlatform() {
+  if (tracing_controller_) {
+    tracing_controller_->StopTracing();
+    tracing_controller_.reset();
+  }
+
   base::LockGuard<base::Mutex> guard(&lock_);
   queue_.Terminate();
   if (initialized_) {
     for (auto i = thread_pool_.begin(); i != thread_pool_.end(); ++i) {
       delete *i;
     }
   }
   for (auto i = main_thread_queue_.begin(); i != main_thread_queue_.end();
        ++i) {
     while (!i->second.empty()) {
       delete i->second.front();
       i->second.pop();
     }
   }
   for (auto i = main_thread_delayed_queue_.begin();
        i != main_thread_delayed_queue_.end(); ++i) {
     while (!i->second.empty()) {
       delete i->second.top().second;
       i->second.pop();
     }
   }
-
-  if (tracing_controller_) {
-    tracing_controller_->StopTracing();
-    delete tracing_controller_;
-  }
 }
 
 
 void DefaultPlatform::SetThreadPoolSize(int thread_pool_size) {
   base::LockGuard<base::Mutex> guard(&lock_);
   DCHECK(thread_pool_size >= 0);
   if (thread_pool_size < 1) {
     thread_pool_size = base::SysInfo::NumberOfProcessors() - 1;
   }
   thread_pool_size_ =
@@ skipping 130 matching lines @@
 
 
 const char* DefaultPlatform::GetCategoryGroupName(
     const uint8_t* category_enabled_flag) {
   static const char dummy[] = "dummy";
   return dummy;
 }
 
 void DefaultPlatform::SetTracingController(
     tracing::TracingController* tracing_controller) {
-  tracing_controller_ = tracing_controller;
+  tracing_controller_.reset(tracing_controller);
 }
 
 size_t DefaultPlatform::NumberOfAvailableBackgroundThreads() {
   return static_cast<size_t>(thread_pool_size_);
 }
 
+void DefaultPlatform::AddTraceStateObserver(TraceStateObserver* observer) {
+  if (!tracing_controller_) return;
+  tracing_controller_->AddTraceStateObserver(observer);
+}
+
+void DefaultPlatform::RemoveTraceStateObserver(TraceStateObserver* observer) {
+  if (!tracing_controller_) return;
+  tracing_controller_->RemoveTraceStateObserver(observer);
+}
+
 }  // namespace platform
 }  // namespace v8