Added UMA stat for tracking accidental navigations on double tap.

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

Index: content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
index e4075f56ebd0d9943cb0317218848331c3cbefb3..6037b4a1a8649d7e8bfadc35251de9ee73d28a2c 100644
--- a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
+++ b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
@@ -23,6 +23,7 @@ import android.os.Build;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.ResultReceiver;
+import android.os.SystemClock;
 import android.provider.Browser;
 import android.provider.Settings;
 import android.text.Editable;
@@ -67,6 +68,7 @@ import org.chromium.content.browser.input.InputMethodManagerWrapper;
 import org.chromium.content.browser.input.InsertionHandleController;
 import org.chromium.content.browser.input.SelectPopupDialog;
 import org.chromium.content.browser.input.SelectionHandleController;
+import org.chromium.content.common.CommandLine;
 import org.chromium.content.common.TraceEvent;
 import org.chromium.ui.ViewAndroid;
 import org.chromium.ui.ViewAndroidDelegate;
@@ -451,6 +453,12 @@ public class ContentViewCore
 
     private ViewAndroid mViewAndroid;
 
+    // Used for tracking UMA ActionAfterDoubleTap to tell user's immediate action after
+    // a double tap.
+    private long mLastDoubleTapTime = 0;
+    private static final long ACTION_AFTER_DOUBLE_TAP_WINDOW = 5000;

[Rick Byers, 2013/10/31 17:53:10]

add an _MS suffix to make it clear this is milliseconds.

[bokan, 2013/10/31 22:31:58]

Done.

+    private static boolean mHasClickDelay;
+
 
     /**
      * Constructs a new ContentViewCore. Embedders must call initialize() after constructing
@@ -768,6 +776,8 @@ public class ContentViewCore
 
         mPid = nativeGetCurrentRenderProcessId(mNativeContentViewCore);
         sendOrientationChangeEvent();
+
+        mHasClickDelay = !CommandLine.getInstance().hasSwitch(CommandLine.DISABLE_CLICK_DELAY);

[Rick Byers, 2013/10/31 17:53:10]

If you move the logic in this file into ContentViewGestureHandler (and plumb the
reportAction... method form here into it), then you could avoid checking this
command line again.  Would be slightly cleaner I think.

[bokan, 2013/10/31 22:31:58]

Done.

     }
 
     @CalledByNative
@@ -1307,12 +1317,47 @@ public class ContentViewCore
         }
     }
 
+    // Enum for immediate user action after a double tap UMA stat.
+    // Be sure to update histograms.xml and the SendActionAfterDoubleTapUma
+    // native method if you change these
+    public static class ActionAfterDoubleTap {
+        public static final int NAVIGATE_BACK = 0;
+        public static final int NAVIGATE_STOP = 1;
+        public static final int NO_ACTION = 2;
+    }
+
+    public void updateActionAfterDoubleTapUMA(int actionType) {
+        long now = SystemClock.uptimeMillis();
+        if (mLastDoubleTapTime > 0
+                && (now - mLastDoubleTapTime) < ACTION_AFTER_DOUBLE_TAP_WINDOW) {
+            nativeSendActionAfterDoubleTapUma(
+                    mNativeContentViewCore,
+                    actionType,
+                    mHasClickDelay);
+        }
+
+        mLastDoubleTapTime = 0;
+    }
+
+    private void updateDoubleTapUmaTimer(long curTimeMs) {
+        if (mLastDoubleTapTime > 0
+                && curTimeMs - mLastDoubleTapTime >= ACTION_AFTER_DOUBLE_TAP_WINDOW) {
+            // Time expired, user took no action (that we care about)
+            nativeSendActionAfterDoubleTapUma(
+                    mNativeContentViewCore,
+                    ActionAfterDoubleTap.NO_ACTION,
+                    mHasClickDelay);
+            mLastDoubleTapTime = 0;
+        }
+    }
+
     @Override
     public boolean sendGesture(int type, long timeMs, int x, int y, Bundle b) {
         if (offerGestureToEmbedder(type)) return false;
         if (mNativeContentViewCore == 0) return false;
         updateTextHandlesForGesture(type);
         updateGestureStateListener(type, b);
+        updateDoubleTapUmaTimer(timeMs);

[Rick Byers, 2013/10/31 17:53:10]

what exactly is this timeMs here - the original event timestamp?  Probably
better to use the current wall clock time here.  Eg. if there was a lot of main
thread jank than the double tap won't have actually happened until awhile after
the event timestamp.

[bokan, 2013/10/31 22:31:58]

It was supposed to be the current time. I've changed to use the current clock
time.

         switch (type) {
             case ContentViewGestureHandler.GESTURE_SHOW_PRESSED_STATE:
                 nativeShowPressState(mNativeContentViewCore, timeMs, x, y);
@@ -1324,6 +1369,7 @@ public class ContentViewCore
                 nativeTapDown(mNativeContentViewCore, timeMs, x, y);
                 return true;
             case ContentViewGestureHandler.GESTURE_DOUBLE_TAP:
+                mLastDoubleTapTime = timeMs;

[Rick Byers, 2013/10/31 17:53:10]

If we didn't report an UMA above but mLastDoubleTapTime is set, then we should
be reporting a NO_ACTION metric here.  Otherwise a constant stream of double tap
events wouldn't report the metric at all...

[bokan, 2013/10/31 22:31:58]

Done.

                 nativeDoubleTap(mNativeContentViewCore, timeMs, x, y);
                 return true;
             case ContentViewGestureHandler.GESTURE_SINGLE_TAP_UP:
@@ -3352,4 +3398,7 @@ public class ContentViewCore
 
     private native void nativeSetAccessibilityEnabled(
             int nativeContentViewCoreImpl, boolean enabled);
+
+    private native void nativeSendActionAfterDoubleTapUma(int nativeContentViewCoreImpl,
+            int type, boolean hasDelay);
 }