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

src/profiler/profiler-listener.cc

 // 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.
 
 #include "src/profiler/profiler-listener.h"
 
 #include "src/deoptimizer.h"
 #include "src/profiler/cpu-profiler.h"
 #include "src/profiler/profile-generator-inl.h"
 #include "src/source-position-table.h"
@@ skipping 301 matching lines @@
     const char* name_prefix, const char* resource_name, int line_number,
     int column_number, JITLineInfoTable* line_info, Address instruction_start) {
   CodeEntry* code_entry =
       new CodeEntry(tag, name, name_prefix, resource_name, line_number,
                     column_number, line_info, instruction_start);
   code_entries_.push_back(code_entry);
   return code_entry;
 }
 
 void ProfilerListener::AddObserver(CodeEventObserver* observer) {
+  base::LockGuard<base::Mutex> guard(&mutex_);
   if (std::find(observers_.begin(), observers_.end(), observer) !=
       observers_.end())
     return;
   observers_.push_back(observer);
 }
 
 void ProfilerListener::RemoveObserver(CodeEventObserver* observer) {
+  base::LockGuard<base::Mutex> guard(&mutex_);
   auto it = std::find(observers_.begin(), observers_.end(), observer);
   if (it == observers_.end()) return;
   observers_.erase(it);
 }
 
 }  // namespace internal
 }  // namespace v8