diff -r 000000000000 -r 6474c204b198 layout/xul/nsScrollbarFrame.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/xul/nsScrollbarFrame.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,193 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//
+// Eric Vaughan
+// Netscape Communications
+//
+// See documentation in associated header file
+//
+
+#include "nsScrollbarFrame.h"
+#include "nsScrollbarButtonFrame.h"
+#include "nsGkAtoms.h"
+#include "nsIScrollableFrame.h"
+#include "nsIScrollbarMediator.h"
+#include "mozilla/LookAndFeel.h"
+#include "nsThemeConstants.h"
+#include "nsRenderingContext.h"
+#include "nsIContent.h"
+
+using namespace mozilla;
+
+//
+// NS_NewScrollbarFrame
+//
+// Creates a new scrollbar frame and returns it
+//
+nsIFrame*
+NS_NewScrollbarFrame (nsIPresShell* aPresShell, nsStyleContext* aContext)
+{
+  return new (aPresShell) nsScrollbarFrame (aPresShell, aContext);
+}
+
+NS_IMPL_FRAMEARENA_HELPERS(nsScrollbarFrame)
+
+NS_QUERYFRAME_HEAD(nsScrollbarFrame)
+  NS_QUERYFRAME_ENTRY(nsScrollbarFrame)
+NS_QUERYFRAME_TAIL_INHERITING(nsBoxFrame)
+
+void
+nsScrollbarFrame::Init(nsIContent* aContent,
+                       nsIFrame*   aParent,
+                       nsIFrame*   aPrevInFlow)
+{
+  nsBoxFrame::Init(aContent, aParent, aPrevInFlow);
+
+  // We want to be a reflow root since we use reflows to move the
+  // slider.  Any reflow inside the scrollbar frame will be a reflow to
+  // move the slider and will thus not change anything outside of the
+  // scrollbar or change the size of the scrollbar frame.
+  mState |= NS_FRAME_REFLOW_ROOT;
+}
+
+nsresult
+nsScrollbarFrame::Reflow(nsPresContext*          aPresContext,
+                         nsHTMLReflowMetrics&     aDesiredSize,
+                         const nsHTMLReflowState& aReflowState,
+                         nsReflowStatus&          aStatus)
+{
+  nsresult rv = nsBoxFrame::Reflow(aPresContext, aDesiredSize, aReflowState, aStatus);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // nsGfxScrollFrame may have told us to shrink to nothing. If so, make sure our
+  // desired size agrees.
+  if (aReflowState.AvailableWidth() == 0) {
+    aDesiredSize.Width() = 0;
+  }
+  if (aReflowState.AvailableHeight() == 0) {
+    aDesiredSize.Height() = 0;
+  }
+
+  return NS_OK;
+}
+
+nsIAtom*
+nsScrollbarFrame::GetType() const
+{
+  return nsGkAtoms::scrollbarFrame;
+}
+
+nsresult
+nsScrollbarFrame::AttributeChanged(int32_t aNameSpaceID,
+                                   nsIAtom* aAttribute,
+                                   int32_t aModType)
+{
+  nsresult rv = nsBoxFrame::AttributeChanged(aNameSpaceID, aAttribute,
+                                             aModType);
+
+  // if the current position changes, notify any nsGfxScrollFrame
+  // parent we may have
+  if (aAttribute != nsGkAtoms::curpos)
+    return rv;
+
+  nsIScrollableFrame* scrollable = do_QueryFrame(GetParent());
+  if (!scrollable)
+    return rv;
+
+  nsCOMPtr<nsIContent> kungFuDeathGrip(mContent);
+  scrollable->CurPosAttributeChanged(mContent);
+  return rv;
+}
+
+NS_IMETHODIMP
+nsScrollbarFrame::HandlePress(nsPresContext* aPresContext,
+                              WidgetGUIEvent* aEvent,
+                              nsEventStatus* aEventStatus)
+{
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsScrollbarFrame::HandleMultiplePress(nsPresContext* aPresContext,
+                                      WidgetGUIEvent* aEvent,
+                                      nsEventStatus* aEventStatus,
+                                      bool aControlHeld)
+{
+  return NS_OK;
+}
+
+NS_IMETHODIMP 
+nsScrollbarFrame::HandleDrag(nsPresContext* aPresContext,
+                             WidgetGUIEvent* aEvent,
+                             nsEventStatus* aEventStatus)
+{
+  return NS_OK;
+}
+
+NS_IMETHODIMP 
+nsScrollbarFrame::HandleRelease(nsPresContext* aPresContext,
+                                WidgetGUIEvent* aEvent,
+                                nsEventStatus* aEventStatus)
+{
+  return NS_OK;
+}
+
+void
+nsScrollbarFrame::SetScrollbarMediatorContent(nsIContent* aMediator)
+{
+  mScrollbarMediator = aMediator;
+}
+
+nsIScrollbarMediator*
+nsScrollbarFrame::GetScrollbarMediator()
+{
+  if (!mScrollbarMediator)
+    return nullptr;
+  nsIFrame* f = mScrollbarMediator->GetPrimaryFrame();
+
+  // check if the frame is a scroll frame. If so, get the scrollable frame
+  // inside it.
+  nsIScrollableFrame* scrollFrame = do_QueryFrame(f);
+  if (scrollFrame) {
+    f = scrollFrame->GetScrolledFrame();
+  }
+
+  nsIScrollbarMediator* sbm = do_QueryFrame(f);
+  return sbm;
+}
+
+nsresult
+nsScrollbarFrame::GetMargin(nsMargin& aMargin)
+{
+  aMargin.SizeTo(0,0,0,0);
+
+  if (LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars) != 0) {
+    nsPresContext* presContext = PresContext();
+    nsITheme* theme = presContext->GetTheme();
+    if (theme) {
+      nsIntSize size;
+      bool isOverridable;
+      nsRefPtr<nsRenderingContext> rc =
+        presContext->PresShell()->CreateReferenceRenderingContext();
+      theme->GetMinimumWidgetSize(rc, this, NS_THEME_SCROLLBAR, &size,
+                                  &isOverridable);
+      if (IsHorizontal()) {
+        aMargin.top = -presContext->DevPixelsToAppUnits(size.height);
+      }
+      else {
+        if (StyleVisibility()->mDirection == NS_STYLE_DIRECTION_RTL) {
+          aMargin.right = -presContext->DevPixelsToAppUnits(size.width);
+        }
+        else {
+          aMargin.left = -presContext->DevPixelsToAppUnits(size.width);
+        }
+      }
+      return NS_OK;
+    }
+  }
+
+  return nsBox::GetMargin(aMargin);
+}