Expose scroll customization for touch to JS (behind REF).

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index c69348e34641b001dad546df2a175dd3c422cf6d..6a805ece91c01398d1d00de3a654aaa5f0a36807 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -30,6 +30,7 @@
 #include "bindings/core/v8/Dictionary.h"
 #include "bindings/core/v8/ExceptionMessages.h"
 #include "bindings/core/v8/ExceptionState.h"
+#include "bindings/core/v8/ToV8.h"
 #include "bindings/core/v8/V8DOMWrapper.h"
 #include "bindings/core/v8/V8PerContextData.h"
 #include "core/CSSValueKeywords.h"
@@ -113,6 +114,7 @@
 #include "core/page/PointerLockController.h"
 #include "core/page/SpatialNavigation.h"
 #include "core/page/scrolling/ScrollState.h"
+#include "core/page/scrolling/ScrollStateCallback.h"
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "core/svg/SVGDocumentExtensions.h"
 #include "core/svg/SVGElement.h"
@@ -470,7 +472,59 @@ void Element::scrollIntoViewIfNeeded(bool centerIfNeeded)
         layoutObject()->scrollRectToVisible(bounds, ScrollAlignment::alignToEdgeIfNeeded, ScrollAlignment::alignToEdgeIfNeeded);
 }
 
-void Element::distributeScroll(ScrollState& scrollState)
+namespace {
+
+class DistributeScrollCallback : public ScrollStateCallback {

[haraken, 2015/06/30 07:08:30]

We should define this in ScrollStateCallback.h (or a dedicated file).

+public:
+    DistributeScrollCallback() { m_callbackType = CallbackType::DISTRIBUTE_SCROLL; }
+    void handleEvent(ScrollState* scrollState)
+    {
+        ASSERT(m_targetElement);
+        ASSERT(scrollState);
+        m_targetElement->nativeDistributeScroll(*scrollState);
+    }
+};
+
+class ApplyScrollCallback : public ScrollStateCallback {

[haraken, 2015/06/30 07:08:30]

Ditto.

+public:
+    ApplyScrollCallback() { m_callbackType = CallbackType::APPLY_SCROLL; }
+    void handleEvent(ScrollState* scrollState)
+    {
+        ASSERT(m_targetElement);
+        ASSERT(scrollState);
+        m_targetElement->nativeApplyScroll(*scrollState);
+    }
+};
+
+} // namespace
+
+void Element::setDistributeScroll(ScrollStateCallback* scrollStateCallback)
+{
+    scrollStateCallback->setCallbackType(ScrollStateCallback::CallbackType::DISTRIBUTE_SCROLL);
+    ensureElementRareData().setDistributeScroll(scrollStateCallback);
+}
+
+ScriptValue Element::distributeScroll(ScriptState* scriptState)
+{
+    if (!hasRareData() || !elementRareData()->getDistributeScroll())
+        setDistributeScroll(new DistributeScrollCallback());

[haraken, 2015/06/30 07:08:30]

In a case where we don't have a customized calback, we want to avoid storing an
empty callback to ElementRareData because it will create an ElementRareData.

Can we just return a native callback without storing anything in
ElementRareData?

+    return elementRareData()->getDistributeScroll()->toScriptValue(scriptState);
+}
+
+void Element::setApplyScroll(ScrollStateCallback* scrollStateCallback)
+{
+    scrollStateCallback->setCallbackType(ScrollStateCallback::CallbackType::APPLY_SCROLL);
+    ensureElementRareData().setApplyScroll(scrollStateCallback);
+}
+
+ScriptValue Element::applyScroll(ScriptState* scriptState)
+{
+    if (!hasRareData() || !elementRareData()->getApplyScroll())
+        setApplyScroll(new ApplyScrollCallback());

[haraken, 2015/06/30 07:08:30]

Ditto.

+    return elementRareData()->getApplyScroll()->toScriptValue(scriptState);
+}
+
+void Element::nativeDistributeScroll(ScrollState& scrollState)
 {
     ASSERT(RuntimeEnabledFeatures::scrollCustomizationEnabled());
     if (scrollState.fullyConsumed())
@@ -490,15 +544,25 @@ void Element::distributeScroll(ScrollState& scrollState)
     const double deltaX = scrollState.deltaX();
     const double deltaY = scrollState.deltaY();
 
-    applyScroll(scrollState);
+    callApplyScroll(scrollState);
 
     if (deltaX != scrollState.deltaX() || deltaY != scrollState.deltaY())
         scrollState.setCurrentNativeScrollingElement(this);
 }
 
-void Element::applyScroll(ScrollState& scrollState)
+void Element::callDistributeScroll(ScrollState& scrollState)
+{
+    if (!hasRareData() || !elementRareData()->getDistributeScroll())
+        nativeDistributeScroll(scrollState);
+    else
+        elementRareData()->getDistributeScroll()->handleEventForElement(*this, &scrollState);
+};
+
+void Element::nativeApplyScroll(ScrollState& scrollState)
 {
     ASSERT(RuntimeEnabledFeatures::scrollCustomizationEnabled());
+    document().updateLayoutIgnorePendingStylesheets();
+
     if (scrollState.fullyConsumed())
         return;
 
@@ -506,8 +570,8 @@ void Element::applyScroll(ScrollState& scrollState)
     const double deltaY = scrollState.deltaY();
     bool scrolled = false;
 
-    // Handle the documentElement separately, as it scrolls the FrameView.
-    if (this == document().documentElement()) {
+    // Handle the scrollingElement separately, as it scrolls the FrameView.
+    if (this == document().scrollingElement()) {
         FloatSize delta(deltaX, deltaY);
         if (document().frame()->applyScrollDelta(delta, scrollState.isBeginning()).didScroll()) {
             scrolled = true;
@@ -542,6 +606,14 @@ void Element::applyScroll(ScrollState& scrollState)
         document().frame()->view()->setWasScrolledByUser(true);
 };
 
+void Element::callApplyScroll(ScrollState& scrollState)
+{
+    if (!hasRareData() || !elementRareData()->getApplyScroll())
+        nativeApplyScroll(scrollState);
+    else
+        elementRareData()->getApplyScroll()->handleEventForElement(*this, &scrollState);
+};
+
 static float localZoomForLayoutObject(LayoutObject& layoutObject)
 {
     // FIXME: This does the wrong thing if two opposing zooms are in effect and canceled each