From 9fe8efb7e3d1820cd7ce8f99332f35534ecc9519 Mon Sep 17 00:00:00 2001
From: Andrew Comminos <acomminos@mozilla.com>
Date: Thu, 18 Jun 2015 12:57:00 -0400
Subject: [PATCH] Bug 1171696 - Don't resize scrollbar thumb when updating its
 position. r=mstange

---
 layout/xul/nsSliderFrame.cpp | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/layout/xul/nsSliderFrame.cpp b/layout/xul/nsSliderFrame.cpp
index a5f51c07012..01d35470b97 100644
--- a/layout/xul/nsSliderFrame.cpp
+++ b/layout/xul/nsSliderFrame.cpp
@@ -727,15 +727,14 @@ nsSliderFrame::CurrentPositionChanged()
 
   // avoid putting the scroll thumb at subpixel positions which cause needless invalidations
   nscoord appUnitsPerPixel = PresContext()->AppUnitsPerDevPixel();
-  nsRect snappedThumbRect = ToAppUnits(newThumbRect.ToNearestPixels(appUnitsPerPixel), appUnitsPerPixel);
+  nsPoint snappedThumbLocation = ToAppUnits(
+      newThumbRect.TopLeft().ToNearestPixels(appUnitsPerPixel),
+      appUnitsPerPixel);
   if (IsHorizontal()) {
-    newThumbRect.x = snappedThumbRect.x;
-    newThumbRect.width = snappedThumbRect.width;
+    newThumbRect.x = snappedThumbLocation.x;
   } else {
-    newThumbRect.y = snappedThumbRect.y;
-    newThumbRect.height = snappedThumbRect.height;
+    newThumbRect.y = snappedThumbLocation.y;
   }
-  newThumbRect = newThumbRect.Intersect(clientRect);
 
   // set the rect
   thumbFrame->SetRect(newThumbRect);