Added UMA stat for tracking accidental navigations on double tap.

content/public/android/java/src/org/chromium/content/browser/ContentViewGestureHandler.java

Index: content/public/android/java/src/org/chromium/content/browser/ContentViewGestureHandler.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/ContentViewGestureHandler.java b/content/public/android/java/src/org/chromium/content/browser/ContentViewGestureHandler.java
index 2ccf09bb4166257089adeb5c709153c5df5d0a6b..0ee9e6a41929197cf90915dd65277681addab7d0 100644
--- a/content/public/android/java/src/org/chromium/content/browser/ContentViewGestureHandler.java
+++ b/content/public/android/java/src/org/chromium/content/browser/ContentViewGestureHandler.java
@@ -336,6 +336,11 @@ class ContentViewGestureHandler implements LongPressDelegate {
          * Show the zoom picker UI.
          */
         public void invokeZoomPicker();
+
+        /**
+         * Send user action for UMA stat tracking
+         */
+        public void sendUserActionUMA(int actionType, boolean clickDelayEnabled);
     }
 
     ContentViewGestureHandler(
@@ -531,6 +536,9 @@ class ContentViewGestureHandler implements LongPressDelegate {
                         // These corner cases should be ignored.
                         if (mLongPressDetector.isInLongPress() || mIgnoreSingleTap) return true;
 
+                        if (!isDoubleTapDisabled() && !mDisableClickDelay)
+                            reportActionForUMA(ContentViewCore.UMAUserAction.DELAYED_TAP);
+
                         int x = (int) e.getX();
                         int y = (int) e.getY();
                         mExtraParamBundleSingleTap.putBoolean(SHOW_PRESS, mShowPressIsCalled);
@@ -1136,12 +1144,17 @@ class ContentViewGestureHandler implements LongPressDelegate {
 
     private boolean sendMotionEventAsGesture(
             int type, MotionEvent event, Bundle extraParams) {
-        return mMotionEventDelegate.sendGesture(type, event.getEventTime(),
+        return sendGesture(type, event.getEventTime(),
             (int) event.getX(), (int) event.getY(), extraParams);
     }
 
     private boolean sendGesture(
             int type, long timeMs, int x, int y, Bundle extraParams) {
+        updateDoubleTapUmaTimer();
+
+        if (type == GESTURE_DOUBLE_TAP)
+            reportActionForUMA(ContentViewCore.UMAUserAction.DOUBLE_TAP);
+
         return mMotionEventDelegate.sendGesture(type, timeMs, x, y, extraParams);
     }
 
@@ -1150,7 +1163,7 @@ class ContentViewGestureHandler implements LongPressDelegate {
         // VSync should only be signalled if the sent gesture was generated from a touch event.
         mSentGestureNeedsVSync = mInputEventsDeliveredAtVSync && mTouchEventHandlingStackDepth > 0;
         mLastVSyncGestureTimeMs = timeMs;
-        return mMotionEventDelegate.sendGesture(type, timeMs, x, y, extraParams);
+        return sendGesture(type, timeMs, x, y, extraParams);
     }
 
     void sendShowPressCancelIfNecessary(MotionEvent e) {
@@ -1267,4 +1280,56 @@ class ContentViewGestureHandler implements LongPressDelegate {
         }
 
     }
+
+
+    public void reportActionForUMA(int actionType) {
+        updateDoubleTapUmaTimer();
+
+        if (actionType == ContentViewCore.UMAUserAction.DOUBLE_TAP) {

[Rick Byers, 2013/11/01 14:45:09]

I think it would be cleaner to just handle this case in a separate function. 
Then you wouldn't need to "pollute" your enum with this special internal-only
value. 

[bokan, 2013/11/01 18:52:44]

Done.

+            // Make sure repeated double taps don't get silently dropped from
+            // the statistics.
+            if (mLastDoubleTapTimeMs > 0)
+                mMotionEventDelegate.sendUserActionUMA(
+                        ContentViewCore.UMAUserAction.NO_ACTION,
+                        !mDisableClickDelay);
+
+            mLastDoubleTapTimeMs = SystemClock.uptimeMillis();
+        } else if (actionType == ContentViewCore.UMAUserAction.DELAYED_TAP) {
+            mMotionEventDelegate.sendUserActionUMA(
+                    actionType, !mDisableClickDelay);
+        } else {
+            if (mLastDoubleTapTimeMs == 0)
+                return;
+
+            long nowMs = SystemClock.uptimeMillis();
+            if ((nowMs - mLastDoubleTapTimeMs)
+                    < ACTION_AFTER_DOUBLE_TAP_WINDOW_MS) {
+                mMotionEventDelegate.sendUserActionUMA(
+                        actionType, !mDisableClickDelay);
+                mLastDoubleTapTimeMs = 0;
+            }
+        }
+    }
+
+    // Watch for the UMA "action after double tap" timer expiring and reset
+    // the timer if necessary.
+    private void updateDoubleTapUmaTimer() {
+        if (mLastDoubleTapTimeMs == 0)
+            return;
+
+        long nowMs = SystemClock.uptimeMillis();
+        if ((nowMs - mLastDoubleTapTimeMs)
+              >= ACTION_AFTER_DOUBLE_TAP_WINDOW_MS) {
+            // Time expired, user took no action (that we care about).
+            mMotionEventDelegate.sendUserActionUMA(
+                    ContentViewCore.UMAUserAction.NO_ACTION,
+                    !mDisableClickDelay);
+            mLastDoubleTapTimeMs = 0;
+        }
+    }
+
+    // Used for tracking UMA ActionAfterDoubleTap to tell user's immediate
+    // action after a double tap.
+    private long mLastDoubleTapTimeMs = 0;
+    private static final long ACTION_AFTER_DOUBLE_TAP_WINDOW_MS = 5000;
 }