Add UMA metric to track the time elapsed since a WebAPK was last launched

base/android/record_histogram.cc

 // Copyright 2014 The Chromium 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 "base/android/record_histogram.h"
 
 #include <stdint.h>
 
 #include <map>
 #include <string>
@@ skipping 297 matching lines @@
       android::ConvertJavaStringToUTF8(env, histogram_name));
   if (histogram == nullptr) {
     // No samples have been recorded for this histogram (yet?).
     return 0;
   }
 
   std::unique_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
   return samples->GetCount(static_cast<int>(sample));
 }
 
+jint GetHistogramTotalCountForTesting(
+    JNIEnv* env,
+    const JavaParamRef<jclass>& clazz,
+    const JavaParamRef<jstring>& histogram_name) {
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(
+      android::ConvertJavaStringToUTF8(env, histogram_name));
+  if (histogram == nullptr) {
+    // No samples have been recorded for this histogram.
+    return 0;
+  }
+
+  std::unique_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
+  return samples->TotalCount();

[Xi Han, 2017/06/14 14:51:06]

Please remove |samples| and return histogram->SnapshotSamples()->TotalCount().

+}
+
 bool RegisterRecordHistogram(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace android
 }  // namespace base