Change the FindHistogram interface of StatisticsRecorder

Review URL: https://chromiumcodereview.appspot.com/10802002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@147269 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 16 insertions, 22 deletions

diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index e176e8f..97069cc 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -79,8 +79,6 @@ Histogram* Histogram::FactoryGet(const std::string& name,
                                  Sample maximum,
                                  size_t bucket_count,
                                  Flags flags) {
-  Histogram* histogram(NULL);
-
   // Defensive code.
   if (minimum < 1)
     minimum = 1;
@@ -91,7 +89,8 @@ Histogram* Histogram::FactoryGet(const std::string& name,
   DCHECK_GT((Sample) bucket_count, 2);
   DCHECK_LE((Sample) bucket_count, maximum - minimum + 2);
 
-  if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
+  Histogram* histogram = StatisticsRecorder::FindHistogram(name);
+  if (!histogram) {
     // Extra variable is not needed... but this keeps this section basically
     // identical to other derived classes in this file (and compiler will
     // optimize away the extra variable.
@@ -806,8 +805,6 @@ Histogram* LinearHistogram::FactoryGet(const std::string& name,
                                        Sample maximum,
                                        size_t bucket_count,
                                        Flags flags) {
-  Histogram* histogram(NULL);
-
   if (minimum < 1)
     minimum = 1;
   if (maximum > kSampleType_MAX - 1)
@@ -817,7 +814,8 @@ Histogram* LinearHistogram::FactoryGet(const std::string& name,
   DCHECK_GT((Sample) bucket_count, 2);
   DCHECK_LE((Sample) bucket_count, maximum - minimum + 2);
 
-  if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
+  Histogram* histogram = StatisticsRecorder::FindHistogram(name);
+  if (!histogram) {
     // To avoid racy destruction at shutdown, the following will be leaked.
     LinearHistogram* tentative_histogram =
         new LinearHistogram(name, minimum, maximum, bucket_count);
@@ -907,9 +905,8 @@ bool LinearHistogram::PrintEmptyBucket(size_t index) const {
 //------------------------------------------------------------------------------
 
 Histogram* BooleanHistogram::FactoryGet(const std::string& name, Flags flags) {
-  Histogram* histogram(NULL);
-
-  if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
+  Histogram* histogram = StatisticsRecorder::FindHistogram(name);
+  if (!histogram) {
     // To avoid racy destruction at shutdown, the following will be leaked.
     BooleanHistogram* tentative_histogram = new BooleanHistogram(name);
     tentative_histogram->InitializeBucketRange();
@@ -941,8 +938,6 @@ BooleanHistogram::BooleanHistogram(const std::string& name)
 Histogram* CustomHistogram::FactoryGet(const std::string& name,
                                        const std::vector<Sample>& custom_ranges,
                                        Flags flags) {
-  Histogram* histogram(NULL);
-
   // Remove the duplicates in the custom ranges array.
   std::vector<int> ranges = custom_ranges;
   ranges.push_back(0);  // Ensure we have a zero value.
@@ -956,7 +951,8 @@ Histogram* CustomHistogram::FactoryGet(const std::string& name,
 
   DCHECK_LT(ranges.back(), kSampleType_MAX);
 
-  if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
+  Histogram* histogram = StatisticsRecorder::FindHistogram(name);
+  if (!histogram) {
     // To avoid racy destruction at shutdown, the following will be leaked.
     CustomHistogram* tentative_histogram = new CustomHistogram(name, ranges);
     tentative_histogram->InitializedCustomBucketRange(ranges);
diff --git a/base/metrics/statistics_recorder.cc b/base/metrics/statistics_recorder.cc
index 37b6f43..384c34f 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -243,18 +243,17 @@ void StatisticsRecorder::GetHistograms(Histograms* output) {
   }
 }
 
-bool StatisticsRecorder::FindHistogram(const std::string& name,
-                                       Histogram** histogram) {
+// static
+Histogram* StatisticsRecorder::FindHistogram(const std::string& name) {
   if (lock_ == NULL)
-    return false;
+    return NULL;
   base::AutoLock auto_lock(*lock_);
   if (!histograms_)
-    return false;
+    return NULL;
   HistogramMap::iterator it = histograms_->find(name);
   if (histograms_->end() == it)
-    return false;
-  *histogram = it->second;
-  return true;
+    return NULL;
+  return it->second;
 }
 
 // private static
diff --git a/base/metrics/statistics_recorder.h b/base/metrics/statistics_recorder.h
index b947c53..ee03f24 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -63,9 +63,8 @@ class BASE_EXPORT StatisticsRecorder {
   static void GetHistograms(Histograms* output);
 
   // Find a histogram by name. It matches the exact name. This method is thread
-  // safe.  If a matching histogram is not found, then the |histogram| is
-  // not changed.
-  static bool FindHistogram(const std::string& query, Histogram** histogram);
+  // safe.  It returns NULL if a matching histogram is not found.
+  static Histogram* FindHistogram(const std::string& name);
 
   static bool dump_on_exit() { return dump_on_exit_; }