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

src/profiler/profiler-listener.h

Index: src/profiler/profiler-listener.h
diff --git a/src/profiler/profiler-listener.h b/src/profiler/profiler-listener.h
index 7e24ceaa8629d4e9bd34446f6237c62008ed43fe..500b7ae6befd11b0942ef3d032423ad185713565 100644
--- a/src/profiler/profiler-listener.h
+++ b/src/profiler/profiler-listener.h
@@ -79,6 +79,7 @@ class ProfilerListener : public CodeEventListener {
   void RecordDeoptInlinedFrames(CodeEntry* entry, AbstractCode* abstract_code);
   Name* InferScriptName(Name* name, SharedFunctionInfo* info);
   V8_INLINE void DispatchCodeEvent(const CodeEventsContainer& evt_rec) {
+    base::LockGuard<base::Mutex> guard(&mutex_);
     for (auto observer : observers_) {
       observer->CodeEventHandler(evt_rec);
     }
@@ -87,6 +88,7 @@ class ProfilerListener : public CodeEventListener {
   StringsStorage function_and_resource_names_;
   std::vector<CodeEntry*> code_entries_;
   std::vector<CodeEventObserver*> observers_;
+  base::Mutex mutex_;
 
   DISALLOW_COPY_AND_ASSIGN(ProfilerListener);
 };