[Herb] Add metrics to track button usage

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

Index: chrome/android/java/src/org/chromium/chrome/browser/metrics/ActivityStopMetrics.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/metrics/ActivityStopMetrics.java b/chrome/android/java/src/org/chromium/chrome/browser/metrics/ActivityStopMetrics.java
new file mode 100644
index 0000000000000000000000000000000000000000..5a3c2dffbdef0d5b7babda4cddda732f43e4e77a
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/metrics/ActivityStopMetrics.java
@@ -0,0 +1,90 @@
+// 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 android.app.Activity;
+import android.support.annotation.IntDef;
+
+import org.chromium.base.ApplicationStatus;
+import org.chromium.base.metrics.RecordHistogram;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * Tracks metrics caused by a particular Activity stopping.
+ */
+public class ActivityStopMetrics {
+    @Retention(RetentionPolicy.SOURCE)
+    @IntDef({
+        STOP_REASON_UNKNOWN,
+        STOP_REASON_BACK_BUTTON,
+        STOP_REASON_RETURN_BUTTON,
+        STOP_REASON_CUSTOM_TAB_STARTED,
+        STOP_REASON_CUSTOM_TAB_STOPPED,
+        STOP_REASON_OTHER_CHROME_ACTIVITY_IN_FOREGROUND,
+        STOP_REASON_COUNT
+    })
+    public @interface StopReason{}
+
+    /** Activity stopped for unknown reasons. */
+    public static final int STOP_REASON_UNKNOWN = 0;
+
+    /** Activity stopped after the user hit the back button. */
+    public static final int STOP_REASON_BACK_BUTTON = 1;
+
+    /** Activity stopped after the user hit the close/return UI button. */
+    public static final int STOP_REASON_RETURN_BUTTON = 2;
+
+    /** Activity stopped because it launched a {@link CustomTabActivity} on top of itself. */
+    public static final int STOP_REASON_CUSTOM_TAB_STARTED = 3;
+
+    /** Activity stopped because its child {@link CustomTabActivity} stopped itself. */
+    public static final int STOP_REASON_CUSTOM_TAB_STOPPED = 4;
+
+    /** Activity stopped because another of Chrome Activities came into focus. */
+    public static final int STOP_REASON_OTHER_CHROME_ACTIVITY_IN_FOREGROUND = 5;
+
+    /** Boundary.  Shouldn't ever be passed to the metrics service. */
+    public static final int STOP_REASON_COUNT = 6;
+
+    /** Name of the histogram that will be recorded. */
+    private static final String HISTOGRAM_NAME = "Android.Activity.ChromeTabbedActivity.StopReason";
+
+    /** Why the Activity is being stopped. */
+    @StopReason private int mStopReason;
+
+    /**
+     * Constructs an {@link ActivityStopMetrics} instance.
+     */
+    public ActivityStopMetrics() {
+        mStopReason = STOP_REASON_COUNT;
+    }
+
+    /**
+     * Records the reason that the parent Activity was stopped.
+     * @param parent Activity that owns this {@link ActivityStopMetrics} instance.
+     */
+    public void onStopWithNative(Activity parent) {
+        if (mStopReason == STOP_REASON_COUNT) {
+            if (parent != ApplicationStatus.getLastTrackedFocusedActivity()) {
+                mStopReason = STOP_REASON_OTHER_CHROME_ACTIVITY_IN_FOREGROUND;
+            } else {
+                mStopReason = STOP_REASON_UNKNOWN;
+            }
+        }
+        RecordHistogram.recordEnumeratedHistogram(HISTOGRAM_NAME, mStopReason, STOP_REASON_COUNT);
+        mStopReason = STOP_REASON_COUNT;
+    }
+
+    /**
+     * Tracks the reason that the parent Activity was stopped.
+     * @param reason Reason the Activity was stopped (see {@link StopReason}).
+     */
+    public void setStopReason(@StopReason int reason) {
+        if (mStopReason != STOP_REASON_COUNT) return;
+        mStopReason = reason;
+    }
+}