[MediaNotification] Add UMA to record user clicking media notifications

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

Index: chrome/android/java/src/org/chromium/chrome/browser/metrics/MediaNotificationUma.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/metrics/MediaNotificationUma.java b/chrome/android/java/src/org/chromium/chrome/browser/metrics/MediaNotificationUma.java
new file mode 100644
index 0000000000000000000000000000000000000000..625c1f59cf5babb0d431dfaaf5e381764021705d
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/metrics/MediaNotificationUma.java
@@ -0,0 +1,40 @@
+// Copyright 2016 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 static org.chromium.chrome.browser.metrics.LaunchMetrics.EnumeratedHistogramSample;
+
+import android.content.Intent;
+
+/**
+ * Helper class to record which kind of media notifications does the user click to go back to
+ * Chrome.
+ */
+public class MediaNotificationUma {
+    public static final int SOURCE_INVALID = -1;
+    public static final int SOURCE_MEDIA = 0;
+    public static final int SOURCE_PRESENTATION = 1;
+    public static final int SOURCE_MEDIA_FLING = 2;
+    public static final int SOURCE_MAX = 3;
+
+    public static final String INTENT_EXTRA_NAME =
+            "org.chromium.chrome.browser.metrics.MediaNotificationUma.EXTRA_CLICK_SOURCE";
+
+    private static final EnumeratedHistogramSample sClickSourceHistogram =
+            new LaunchMetrics.EnumeratedHistogramSample(
+                    "Media.Notification.Click", SOURCE_MAX);
+
+    /**
+     * Record the UMA as specified by {@link intent}. The {@link intent} should contain intent extra
+     * of name {@link INTENT_EXTRA_NAME} indicating the type.
+     * @param intent The intent starting the activity.
+     */
+    public static void recordClickSource(Intent intent) {
+        if (intent == null) return;
+        int source = intent.getIntExtra(INTENT_EXTRA_NAME, SOURCE_INVALID);
+        if (source == SOURCE_INVALID || source >= SOURCE_MAX) return;
+        sClickSourceHistogram.record(source);
+    }
+}