From 2c527faa56cdc3a05148182bdc265510d0788ac5 Mon Sep 17 00:00:00 2001
From: Shih-Chiang Chien <schien@mozilla.com>
Date: Fri, 11 Jan 2013 11:02:02 +0100
Subject: [PATCH] Bug 828367 - APZC should not perform scrolling if BES detects
 panning distance is too small. r=cjones.

---
 dom/browser-element/BrowserElementScrolling.js | 13 ++++++++++---
 gfx/layers/ipc/AsyncPanZoomController.cpp      |  2 +-
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/dom/browser-element/BrowserElementScrolling.js b/dom/browser-element/BrowserElementScrolling.js
index 84ee9c16650..71d7c156426 100644
--- a/dom/browser-element/BrowserElementScrolling.js
+++ b/dom/browser-element/BrowserElementScrolling.js
@@ -233,10 +233,19 @@ const ContentPanning = {
     }
 
     let isPan = KineticPanning.isPan();
+    if (!isPan) {
+      // If panning distance is not large enough, both BES and APZC
+      // should not perform scrolling
+      evt.preventDefault();
+      return;
+    }
+
+    let isScroll = this.scrollCallback(delta.scale(-1));
+
     if (this.detectingScrolling) {
       this.detectingScrolling = false;
       // Stop async-pan-zooming if the user is panning the subframe.
-      if (isPan) {
+      if (isScroll) {
         // We're going to drive synchronously scrolling an inner frame.
         Services.obs.notifyObservers(docShell, 'cancel-default-pan-zoom', null);
       } else {
@@ -246,8 +255,6 @@ const ContentPanning = {
       }
     }
 
-    this.scrollCallback(delta.scale(-1));
-
     // If a pan action happens, cancel the active state of the
     // current target.
     if (!this.panning && isPan) {
diff --git a/gfx/layers/ipc/AsyncPanZoomController.cpp b/gfx/layers/ipc/AsyncPanZoomController.cpp
index 06598773c17..7176b2a1ad1 100644
--- a/gfx/layers/ipc/AsyncPanZoomController.cpp
+++ b/gfx/layers/ipc/AsyncPanZoomController.cpp
@@ -1421,7 +1421,7 @@ void AsyncPanZoomController::ContentReceivedTouch(bool aPreventDefault) {
 
     while (!mTouchQueue.IsEmpty()) {
       // we need to reset mDelayPanning before handling scrolling gesture.
-      if (mTouchQueue[0].mType == MultiTouchInput::MULTITOUCH_MOVE) {
+      if (!aPreventDefault && mTouchQueue[0].mType == MultiTouchInput::MULTITOUCH_MOVE) {
         mDelayPanning = false;
       }
       if (!aPreventDefault) {