Bug 859305 - Stop the browser app from panning the page when the user drags an <input type=range>'s thumb in the out-of-process case. r=smaug

layout/base/nsPresShell.cpp

@@ -6930,7 +6930,8 @@ PresShell::DispatchTouchEvent(nsEvent *aEvent,
     tmpStatus = nsEventStatus_eIgnore;
     nsEventDispatcher::Dispatch(targetPtr, context,
                                 &newEvent, nullptr, &tmpStatus, aEventCB);
-    if (nsEventStatus_eConsumeNoDefault == tmpStatus) {
+    if (nsEventStatus_eConsumeNoDefault == tmpStatus ||
+        newEvent.mFlags.mMultipleActionsPrevented) {
       preventDefault = true;
     }
 

layout/forms/nsRangeFrame.cpp

@@ -52,6 +52,34 @@ NS_QUERYFRAME_HEAD(nsRangeFrame)
   NS_QUERYFRAME_ENTRY(nsIAnonymousContentCreator)
 NS_QUERYFRAME_TAIL_INHERITING(nsContainerFrame)
 
+void
+nsRangeFrame::Init(nsIContent* aContent,
+                   nsIFrame*   aParent,
+                   nsIFrame*   aPrevInFlow)
+{
+  // B2G's AsyncPanZoomController::ReceiveInputEvent handles touch events
+  // without checking whether the out-of-process document that it controls
+  // will handle them, unless it has been told that the document might do so.
+  // This is for perf reasons, otherwise it has to wait for the event to be
+  // round-tripped to the other process and back, delaying panning, etc.
+  // We must call SetHasTouchEventListeners() in order to get APZC to wait
+  // until the event has been round-tripped and check whether it has been
+  // handled, otherwise B2G will end up panning the document when the user
+  // tries to drag our thumb.
+  //
+  nsIPresShell* presShell = PresContext()->GetPresShell();
+  if (presShell) {
+    nsIDocument* document = presShell->GetDocument();
+    if (document) {
+      nsPIDOMWindow* innerWin = document->GetInnerWindow();
+      if (innerWin) {
+        innerWin->SetHasTouchEventListeners();
+      }
+    }
+  }
+  return nsContainerFrame::Init(aContent, aParent, aPrevInFlow);
+}
+
 void
 nsRangeFrame::DestroyFrom(nsIFrame* aDestructRoot)
 {

layout/forms/nsRangeFrame.h

@@ -29,6 +29,10 @@ public:
   NS_DECL_FRAMEARENA_HELPERS
 
   // nsIFrame overrides
+  virtual void Init(nsIContent*      aContent,
+                    nsIFrame*        aParent,
+                    nsIFrame*        aPrevInFlow) MOZ_OVERRIDE;
+
   virtual void DestroyFrom(nsIFrame* aDestructRoot) MOZ_OVERRIDE;
 
   void BuildDisplayList(nsDisplayListBuilder*   aBuilder,