diff --git a/content/base/src/nsGenericElement.cpp b/content/base/src/nsGenericElement.cpp
index 7e1709c7a4df..f942f8954458 100644
--- a/content/base/src/nsGenericElement.cpp
+++ b/content/base/src/nsGenericElement.cpp
@@ -2133,11 +2133,8 @@ nsGenericElement::SetScrollTop(PRInt32 aScrollTop)
   nsIScrollableFrame* sf = GetScrollFrame();
   if (sf) {
     nsPoint pt = sf->GetScrollPosition();
-    pt.y = nsPresContext::CSSPixelsToAppUnits(aScrollTop);
-    nscoord halfPixel = nsPresContext::CSSPixelsToAppUnits(0.5f);
-    // Don't allow pt.y + halfPixel since that would round up to the next CSS pixel.
-    nsRect range(pt.x, pt.y - halfPixel, 0, halfPixel*2 - 1);
-    sf->ScrollTo(pt, nsIScrollableFrame::INSTANT, &range);
+    sf->ScrollToCSSPixels(nsIntPoint(nsPresContext::AppUnitsToIntCSSPixels(pt.x),
+                                     aScrollTop));
   }
   return NS_OK;
 }
@@ -2166,11 +2163,8 @@ nsGenericElement::SetScrollLeft(PRInt32 aScrollLeft)
   nsIScrollableFrame* sf = GetScrollFrame();
   if (sf) {
     nsPoint pt = sf->GetScrollPosition();
-    pt.x = nsPresContext::CSSPixelsToAppUnits(aScrollLeft);
-    nscoord halfPixel = nsPresContext::CSSPixelsToAppUnits(0.5f);
-    // Don't allow pt.x + halfPixel since that would round up to the next CSS pixel.
-    nsRect range(pt.x - halfPixel, pt.y, halfPixel*2 - 1, 0);
-    sf->ScrollTo(pt, nsIScrollableFrame::INSTANT, &range);
+    sf->ScrollToCSSPixels(nsIntPoint(aScrollLeft,
+                                     nsPresContext::AppUnitsToIntCSSPixels(pt.y)));
   }
   return NS_OK;
 }
diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index a3e3eadeda99..374a68797cb5 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -5328,12 +5328,7 @@ nsGlobalWindow::ScrollTo(PRInt32 aXScroll, PRInt32 aYScroll)
     if (aYScroll > maxpx) {
       aYScroll = maxpx;
     }
-    nsPoint pt(nsPresContext::CSSPixelsToAppUnits(aXScroll),
-               nsPresContext::CSSPixelsToAppUnits(aYScroll));
-    nscoord halfPixel = nsPresContext::CSSPixelsToAppUnits(0.5f);
-    // Don't allow pt.x/y + halfPixel since that would round up to the next CSS pixel.
-    nsRect range(pt.x - halfPixel, pt.y - halfPixel, halfPixel*2 - 1, halfPixel*2 - 1);
-    sf->ScrollTo(pt, nsIScrollableFrame::INSTANT, &range);
+    sf->ScrollToCSSPixels(nsIntPoint(aXScroll, aYScroll));
   }
 
   return NS_OK;
diff --git a/layout/generic/nsGfxScrollFrame.cpp b/layout/generic/nsGfxScrollFrame.cpp
index 0c1ac592a41c..096078a71efb 100644
--- a/layout/generic/nsGfxScrollFrame.cpp
+++ b/layout/generic/nsGfxScrollFrame.cpp
@@ -1724,6 +1724,31 @@ nsGfxScrollFrameInner::AsyncScrollCallback(void* anInstance, mozilla::TimeStamp
   self->ScrollToImpl(self->mDestination, range);
 }
 
+void
+nsGfxScrollFrameInner::ScrollToCSSPixels(nsIntPoint aScrollPosition)
+{
+  nsPoint current = GetScrollPosition();
+  nsPoint pt(nsPresContext::CSSPixelsToAppUnits(aScrollPosition.x),
+             nsPresContext::CSSPixelsToAppUnits(aScrollPosition.y));
+  nscoord halfPixel = nsPresContext::CSSPixelsToAppUnits(0.5f);
+  nsRect range(pt.x - halfPixel, pt.y - halfPixel, 2*halfPixel - 1, 2*halfPixel - 1);
+  if (nsPresContext::AppUnitsToIntCSSPixels(current.x) == aScrollPosition.x) {
+    pt.x = current.x;
+    range.x = pt.x;
+    range.width = 0;
+  } else {
+    // current.x must be outside 'range', so we must move in the correct direction.
+  }
+  if (nsPresContext::AppUnitsToIntCSSPixels(current.y) == aScrollPosition.y) {
+    pt.y = current.y;
+    range.y = pt.y;
+    range.height = 0;
+  } else {
+    // current.y must be outside 'range', so we must move in the correct direction.
+  }
+  ScrollTo(pt, nsIScrollableFrame::INSTANT, &range);
+}
+
 /*
  * this method wraps calls to ScrollToImpl(), either in one shot or incrementally,
  *  based on the setting of the smoothness scroll pref
diff --git a/layout/generic/nsGfxScrollFrame.h b/layout/generic/nsGfxScrollFrame.h
index 63caddef8a0b..1fa67f832a91 100644
--- a/layout/generic/nsGfxScrollFrame.h
+++ b/layout/generic/nsGfxScrollFrame.h
@@ -195,6 +195,7 @@ public:
                 const nsRect* aRange = nsnull) {
     ScrollToWithOrigin(aScrollPosition, aMode, nsGkAtoms::other, aRange);
   }
+  void ScrollToCSSPixels(nsIntPoint aScrollPosition);
   void ScrollToImpl(nsPoint aScrollPosition, const nsRect& aRange);
   void ScrollVisual(nsPoint aOldScrolledFramePosition);
   void ScrollBy(nsIntPoint aDelta, nsIScrollableFrame::ScrollUnit aUnit,
@@ -505,6 +506,9 @@ public:
                         const nsRect* aRange = nsnull) {
     mInner.ScrollTo(aScrollPosition, aMode, aRange);
   }
+  virtual void ScrollToCSSPixels(nsIntPoint aScrollPosition) {
+    mInner.ScrollToCSSPixels(aScrollPosition);
+  }
   virtual void ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,
                         nsIntPoint* aOverflow, nsIAtom *aOrigin = nsnull) {
     mInner.ScrollBy(aDelta, aUnit, aMode, aOverflow, aOrigin);
@@ -747,6 +751,9 @@ public:
                         const nsRect* aRange = nsnull) {
     mInner.ScrollTo(aScrollPosition, aMode, aRange);
   }
+  virtual void ScrollToCSSPixels(nsIntPoint aScrollPosition) {
+    mInner.ScrollToCSSPixels(aScrollPosition);
+  }
   virtual void ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,
                         nsIntPoint* aOverflow, nsIAtom *aOrigin = nsnull) {
     mInner.ScrollBy(aDelta, aUnit, aMode, aOverflow, aOrigin);
diff --git a/layout/generic/nsIScrollableFrame.h b/layout/generic/nsIScrollableFrame.h
index 1c07921835fc..cbbccdf4c856 100644
--- a/layout/generic/nsIScrollableFrame.h
+++ b/layout/generic/nsIScrollableFrame.h
@@ -156,6 +156,15 @@ public:
    */
   virtual void ScrollTo(nsPoint aScrollPosition, ScrollMode aMode,
                         const nsRect* aRange = nsnull) = 0;
+  /**
+   * Scrolls to a particular position in integer CSS pixels.
+   * Keeps the exact current horizontal or vertical position if the current
+   * position, rounded to CSS pixels, matches aScrollPosition. If
+   * aScrollPosition.x/y is different from the current CSS pixel position,
+   * makes sure we only move in the direction given by the difference.
+   * The scroll mode is INSTANT.
+   */
+  virtual void ScrollToCSSPixels(nsIntPoint aScrollPosition) = 0;
   /**
    * When scrolling by a relative amount, we can choose various units.
    */
diff --git a/layout/reftests/scrolling/reftest.list b/layout/reftests/scrolling/reftest.list
index 6b0f62cc55ae..98a2581aca06 100644
--- a/layout/reftests/scrolling/reftest.list
+++ b/layout/reftests/scrolling/reftest.list
@@ -8,6 +8,7 @@ random-if(Android) HTTP == image-1.html image-1.html?ref
 HTTP == opacity-mixed-scrolling-1.html opacity-mixed-scrolling-1.html?ref
 random-if(cocoaWidget) HTTP == opacity-mixed-scrolling-2.html opacity-mixed-scrolling-2.html?ref # see bug 625357
 HTTP == simple-1.html simple-1.html?ref
+HTTP == subpixel-1.html#d subpixel-1-ref.html#d
 HTTP == text-1.html text-1.html?ref
 HTTP == text-2.html?up text-2.html?ref
 HTTP == transformed-1.html transformed-1.html?ref
diff --git a/layout/reftests/scrolling/subpixel-1-ref.html b/layout/reftests/scrolling/subpixel-1-ref.html
new file mode 100644
index 000000000000..52ec2c54a579
--- /dev/null
+++ b/layout/reftests/scrolling/subpixel-1-ref.html
@@ -0,0 +1,7 @@
+<!DOCTYPE HTML>
+<html>
+<body style="margin:0">
+<div style="height:1205.6px"></div>
+<div id="d" style="height:0.6px; background:red"></div>
+</body>
+</html>
diff --git a/layout/reftests/scrolling/subpixel-1.html b/layout/reftests/scrolling/subpixel-1.html
new file mode 100644
index 000000000000..a0bac5f6a660
--- /dev/null
+++ b/layout/reftests/scrolling/subpixel-1.html
@@ -0,0 +1,12 @@
+<!DOCTYPE HTML>
+<html>
+<body style="margin:0" onload="doTest()">
+<div style="height:1205.6px"></div>
+<div id="d" style="height:0.6px; background:red"></div>
+<script>
+function doTest() {
+  window.scrollTo(0, document.documentElement.scrollTop);
+}
+</script>
+</body>
+</html>