[turbofan] Add a mutex for recording compilation statistics

There was previously a race between different phases recording their
first entry -- and thus, their insert order -- on the main and
concurrent-compilation thread. This would later manifest as a segfault
when creating the sorted array of phases for --turbo-stats (as two
phases would have the same insert order and so there would be a gap in
the array).

Review-Url: https://codereview.chromium.org/2572713003
Cr-Commit-Position: refs/heads/master@{#41669}

src/compilation-statistics.cc

@@ -14,6 +14,8 @@ namespace internal {
 void CompilationStatistics::RecordPhaseStats(const char* phase_kind_name,
                                              const char* phase_name,
                                              const BasicStats& stats) {
+  base::LockGuard<base::Mutex> guard(&record_mutex_);
+
   std::string phase_name_str(phase_name);
   auto it = phase_map_.find(phase_name_str);
   if (it == phase_map_.end()) {
@@ -26,6 +28,8 @@ void CompilationStatistics::RecordPhaseStats(const char* phase_kind_name,
 
 void CompilationStatistics::RecordPhaseKindStats(const char* phase_kind_name,
                                                  const BasicStats& stats) {
+  base::LockGuard<base::Mutex> guard(&record_mutex_);
+
   std::string phase_kind_name_str(phase_kind_name);
   auto it = phase_kind_map_.find(phase_kind_name_str);
   if (it == phase_kind_map_.end()) {
@@ -39,6 +43,8 @@ void CompilationStatistics::RecordPhaseKindStats(const char* phase_kind_name,
 
 void CompilationStatistics::RecordTotalStats(size_t source_size,
                                              const BasicStats& stats) {
+  base::LockGuard<base::Mutex> guard(&record_mutex_);
+
   source_size += source_size;
   total_stats_.Accumulate(stats);
 }

src/compilation-statistics.h

@@ -80,6 +80,7 @@ class CompilationStatistics final : public Malloced {
   TotalStats total_stats_;
   PhaseKindMap phase_kind_map_;
   PhaseMap phase_map_;
+  base::Mutex record_mutex_;
 
   DISALLOW_COPY_AND_ASSIGN(CompilationStatistics);
 };