Remove static locals from histograms.

webrtc/system_wrappers/source/metrics_default.cc

 // Copyright (c) 2014 The WebRTC 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 in the root of the source
 // tree. An additional intellectual property rights grant can be found
 // in the file PATENTS.  All contributing project authors may
 // be found in the AUTHORS file in the root of the source tree.
 //
 
 #include "webrtc/system_wrappers/include/metrics_default.h"
@@ skipping 235 matching lines @@
   return map->GetEnumerationHistogram(name, boundary);
 }
 
 const std::string& GetHistogramName(Histogram* histogram_pointer) {
   RtcHistogram* ptr = reinterpret_cast<RtcHistogram*>(histogram_pointer);
   return ptr->name();
 }
 
 // Fast path. Adds |sample| to cached |histogram_pointer|.
 void HistogramAdd(Histogram* histogram_pointer, int sample) {
+  if (g_rtc_histogram_map == nullptr) {
+    // Histograms are disabled, so the pointer is invalid. Check on this instead
+    // of histogram_pointer being NULL so that we don't accidentally miss
+    // instances where HistogramAdd(histogram_, sample) is called with
+    // histogram_ uninitialized.
+    //
+    // This doesn't happen in Chromium since base::Histogram::FactoryGet and
+    // base::LinearHistogram::FactoryGet always return valid base::HistogramBase
+    // pointers. We could consider returning a null object, but having
+    // RtcHistogram virtual makes function calls to it slower.
+    return;
+  }
   RtcHistogram* ptr = reinterpret_cast<RtcHistogram*>(histogram_pointer);
   ptr->Add(sample);
 }
 
 SampleInfo::SampleInfo(const std::string& name,
                        int min,
                        int max,
                        size_t bucket_count)
     : name(name), min(min), max(max), bucket_count(bucket_count) {}
 
 SampleInfo::~SampleInfo() {}
 
 // Implementation of global functions in metrics_default.h.
 void Enable() {
+  // TODO(pbos): Make sure that no callers have called HistogramFactoryGet*,
+  // HistogramAdd or GetMap() at this point.
   RTC_DCHECK(g_rtc_histogram_map == nullptr);
 #if RTC_DCHECK_IS_ON
   RTC_DCHECK_EQ(0, rtc::AtomicOps::AcquireLoad(&g_rtc_histogram_called));
 #endif
   CreateMap();
 }
 
 void GetAndReset(
     std::map<std::string, std::unique_ptr<SampleInfo>>* histograms) {
   histograms->clear();
@@ skipping 18 matching lines @@
   return map ? map->NumSamples(name) : 0;
 }
 
 int MinSample(const std::string& name) {
   RtcHistogramMap* map = GetMap();
   return map ? map->MinSample(name) : -1;
 }
 
 }  // namespace metrics
 }  // namespace webrtc