[MediaNotification] Add UMA to record user clicking media notifications

chrome/android/java/src/org/chromium/chrome/browser/metrics/LaunchMetrics.java

 // Copyright 2015 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.
 
 package org.chromium.chrome.browser.metrics;
 
 import android.util.Pair;
 
 import org.chromium.base.annotations.JNINamespace;
 import org.chromium.base.metrics.RecordHistogram;
@@ skipping 66 matching lines @@
 
         @Override
         protected void commitAndClear() {
             for (Integer sample : mSamples) {
                 RecordHistogram.recordSparseSlowlyHistogram(mHistogramName, sample);
             }
             mSamples.clear();
         }
     }
 
+    /** Caches a set of enumerated histogram samples. */
+    public static class EnumeratedHistogramSample extends CachedHistogram {
+        private final List<Integer> mSamples = new ArrayList<Integer>();
+        private final int mMaxValue;
+
+        public EnumeratedHistogramSample(String histogramName, int maxValue) {
+            super(histogramName);
+            mMaxValue = maxValue;
+        }
+
+        public void record(int sample) {
+            mSamples.add(sample);
+        }
+
+        @Override
+        protected void commitAndClear() {
+            for (Integer sample : mSamples) {
+                RecordHistogram.recordEnumeratedHistogram(mHistogramName, sample, mMaxValue);
+            }
+            mSamples.clear();
+        }
+    }
+
     // Each list item is a pair of the url and where it was added from e.g. from the add to
     // homescreen menu item, an app banner, or unknown. The mapping of int source values to
     // their string names is found in the C++ ShortcutInfo struct.
     private static final List<Pair<String, Integer>> sActivityUrls =
             new ArrayList<Pair<String, Integer>>();
     private static final List<Pair<String, Integer>> sTabUrls =
             new ArrayList<Pair<String, Integer>>();
 
     private static final List<Long> sWebappHistogramTimes = new ArrayList<Long>();
 
@@ skipping 47 matching lines @@
         }
         sWebappHistogramTimes.clear();
 
         // Record generic cached events.
         for (CachedHistogram event : CachedHistogram.sEvents) event.commitAndClear();
     }
 
     private static native void nativeRecordLaunch(
             boolean standalone, String url, int source, WebContents webContents);
 }