[profiler] Allow thread-safe access to add/remove code event observers.

src/code-events.h

 // Copyright 2016 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.
 
 #ifndef V8_CODE_EVENTS_H_
 #define V8_CODE_EVENTS_H_
 
 #include <unordered_set>
 
+#include "src/base/platform/mutex.h"
 #include "src/globals.h"
 
 namespace v8 {
 namespace internal {
 
 class AbstractCode;
 class Name;
 class SharedFunctionInfo;
 class String;
 
@@ skipping 87 matching lines @@
   virtual void CodeDeoptEvent(Code* code, Address pc, int fp_to_sp_delta) = 0;
 };
 
 class CodeEventDispatcher {
  public:
   using LogEventsAndTags = CodeEventListener::LogEventsAndTags;
 
   CodeEventDispatcher() {}
 
   bool AddListener(CodeEventListener* listener) {
+    base::LockGuard<base::Mutex> guard(&mutex_);
     return listeners_.insert(listener).second;
   }
   void RemoveListener(CodeEventListener* listener) {
+    base::LockGuard<base::Mutex> guard(&mutex_);
     listeners_.erase(listener);
   }
 
-#define CODE_EVENT_DISPATCH(code) \
+#define CODE_EVENT_DISPATCH(code)              \
+  if (listeners_.empty()) return;              \
+  base::LockGuard<base::Mutex> guard(&mutex_); \
   for (auto it = listeners_.begin(); it != listeners_.end(); ++it) (*it)->code
 
   void CodeCreateEvent(LogEventsAndTags tag, AbstractCode* code,
                        const char* comment) {
     CODE_EVENT_DISPATCH(CodeCreateEvent(tag, code, comment));
   }
   void CodeCreateEvent(LogEventsAndTags tag, AbstractCode* code, Name* name) {
     CODE_EVENT_DISPATCH(CodeCreateEvent(tag, code, name));
   }
   void CodeCreateEvent(LogEventsAndTags tag, AbstractCode* code,
@@ skipping 32 matching lines @@
   void CodeDisableOptEvent(AbstractCode* code, SharedFunctionInfo* shared) {
     CODE_EVENT_DISPATCH(CodeDisableOptEvent(code, shared));
   }
   void CodeDeoptEvent(Code* code, Address pc, int fp_to_sp_delta) {
     CODE_EVENT_DISPATCH(CodeDeoptEvent(code, pc, fp_to_sp_delta));
   }
 #undef CODE_EVENT_DISPATCH
 
  private:
   std::unordered_set<CodeEventListener*> listeners_;
+  base::Mutex mutex_;
 
   DISALLOW_COPY_AND_ASSIGN(CodeEventDispatcher);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CODE_EVENTS_H_