Implement CSS: scroll-boundary-behavior

third_party/WebKit/Source/core/input/ScrollManager.cpp

Index: third_party/WebKit/Source/core/input/ScrollManager.cpp
diff --git a/third_party/WebKit/Source/core/input/ScrollManager.cpp b/third_party/WebKit/Source/core/input/ScrollManager.cpp
index 0d4a7cb180e276e187db3c6488917ace6589fea7..5a349f7fd3a88c8bc651f895e2111e3dbc66e05c 100644
--- a/third_party/WebKit/Source/core/input/ScrollManager.cpp
+++ b/third_party/WebKit/Source/core/input/ScrollManager.cpp
@@ -6,6 +6,7 @@
 
 #include <memory>
 #include "core/dom/DOMNodeIds.h"
+#include "core/dom/NodeComputedStyle.h"
 #include "core/events/GestureEvent.h"
 #include "core/frame/BrowserControls.h"
 #include "core/frame/LocalFrameView.h"
@@ -93,6 +94,8 @@ void ScrollManager::RecomputeScrollChain(const Node& start_node,
   DCHECK(start_node.GetLayoutObject());
   LayoutBox* cur_box = start_node.GetLayoutObject()->EnclosingBox();
   Element* document_element = frame_->GetDocument()->documentElement();
+  bool x_dominated =
+      std::abs(scroll_state.deltaXHint()) > std::abs(scroll_state.deltaYHint());
 
   // Scrolling propagates along the containing block chain and ends at the
   // RootScroller element. The RootScroller element will have a custom
@@ -117,6 +120,14 @@ void ScrollManager::RecomputeScrollChain(const Node& start_node,
       if (IsViewportScrollingElement(*cur_element) ||
           cur_element == document_element)
         break;
+
+      if ((x_dominated &&
+           cur_element->GetComputedStyle()->ScrollBoundaryBehaviorX() !=
+               EScrollBoundaryBehavior::kAuto) ||
+          (!x_dominated &&
+           cur_element->GetComputedStyle()->ScrollBoundaryBehaviorY() !=
+               EScrollBoundaryBehavior::kAuto))
+        break;
     }
 
     cur_box = cur_box->ContainingBlock();