--- a/gfx/thebes/gfxPrefs.h
+++ b/gfx/thebes/gfxPrefs.h
@@ -206,16 +206,20 @@ private:
   DECL_GFX_PREF(Live, "general.smoothScroll",                  SmoothScrollEnabled, bool, true);
   DECL_GFX_PREF(Live, "general.smoothScroll.durationToIntervalRatio",
                 SmoothScrollDurationToIntervalRatio, int32_t, 200);
   DECL_GFX_PREF(Live, "general.smoothScroll.mouseWheel",       WheelSmoothScrollEnabled, bool, true);
   DECL_GFX_PREF(Live, "general.smoothScroll.mouseWheel.durationMaxMS",
                 WheelSmoothScrollMaxDurationMs, int32_t, 400);
   DECL_GFX_PREF(Live, "general.smoothScroll.mouseWheel.durationMinMS",
                 WheelSmoothScrollMinDurationMs, int32_t, 200);
+  DECL_GFX_PREF(Live, "general.smoothScroll.currentVelocityWeighting",
+                SmoothScrollCurrentVelocityWeighting, float, 0.25);
+  DECL_GFX_PREF(Live, "general.smoothScroll.stopDecelerationWeighting",
+                SmoothScrollStopDecelerationWeighting, float, 0.4);
 
   DECL_GFX_PREF(Once, "gfx.android.rgb16.force",               AndroidRGB16Force, bool, false);
 #if defined(ANDROID)
   DECL_GFX_PREF(Once, "gfx.apitrace.enabled",                  UseApitrace, bool, false);
 #endif
 #if defined(RELEASE_BUILD)
   // "Skip" means this is locked to the default value in beta and release.
   DECL_GFX_PREF(Skip, "gfx.blocklist.all",                     BlocklistAll, int32_t, 0);

--- a/layout/generic/AsyncScrollBase.cpp
+++ b/layout/generic/AsyncScrollBase.cpp
@@ -1,14 +1,15 @@
 /* -*- 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/. */
 
 #include "AsyncScrollBase.h"
+#include "gfxPrefs.h"
 
 using namespace mozilla;
 
 AsyncScrollBase::AsyncScrollBase(nsPoint aStartPos)
  : mIsFirstIteration(true)
  , mStartPos(aStartPos)
 {
 }
@@ -72,36 +73,33 @@ AsyncScrollBase::InitializeHistory(TimeS
 
   // Longest relevant interval (which results in maximum duration)
   TimeDuration maxDelta = TimeDuration::FromMilliseconds(mOriginMaxMS / mIntervalRatio);
   mPrevEventTime[0] = aTime              - maxDelta;
   mPrevEventTime[1] = mPrevEventTime[0]  - maxDelta;
   mPrevEventTime[2] = mPrevEventTime[1]  - maxDelta;
 }
 
-const double kCurrentVelocityWeighting = 0.25;
-const double kStopDecelerationWeighting = 0.4;
-
 void
 AsyncScrollBase::InitTimingFunction(nsSMILKeySpline& aTimingFunction,
                                     nscoord aCurrentPos,
                                     nscoord aCurrentVelocity,
                                     nscoord aDestination)
 {
-  if (aDestination == aCurrentPos || kCurrentVelocityWeighting == 0) {
-    aTimingFunction.Init(0, 0, 1 - kStopDecelerationWeighting, 1);
+  if (aDestination == aCurrentPos || gfxPrefs::SmoothScrollCurrentVelocityWeighting() == 0) {
+    aTimingFunction.Init(0, 0, 1 - gfxPrefs::SmoothScrollStopDecelerationWeighting(), 1);
     return;
   }
 
   const TimeDuration oneSecond = TimeDuration::FromSeconds(1);
   double slope = aCurrentVelocity * (mDuration / oneSecond) / (aDestination - aCurrentPos);
   double normalization = sqrt(1.0 + slope * slope);
-  double dt = 1.0 / normalization * kCurrentVelocityWeighting;
-  double dxy = slope / normalization * kCurrentVelocityWeighting;
-  aTimingFunction.Init(dt, dxy, 1 - kStopDecelerationWeighting, 1);
+  double dt = 1.0 / normalization * gfxPrefs::SmoothScrollCurrentVelocityWeighting();
+  double dxy = slope / normalization * gfxPrefs::SmoothScrollCurrentVelocityWeighting();
+  aTimingFunction.Init(dt, dxy, 1 - gfxPrefs::SmoothScrollStopDecelerationWeighting(), 1);
 }
 
 nsPoint
 AsyncScrollBase::PositionAt(TimeStamp aTime) const
 {
   double progressX = mTimingFunctionX.GetSplineValue(ProgressAt(aTime));
   double progressY = mTimingFunctionY.GetSplineValue(ProgressAt(aTime));
   return nsPoint(NSToCoordRound((1 - progressX) * mStartPos.x + progressX * mDestination.x),

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -2122,16 +2122,19 @@ pref("general.smoothScroll.pages", true)
 pref("general.smoothScroll.scrollbars", true);
 pref("general.smoothScroll.other", true);
 // To connect consecutive scroll events into a continuous flow, the animation's duration
 // should be longer than scroll events intervals (or else the scroll will stop
 // before the next event arrives - we're guessing next interval by averaging recent
 // intervals).
 // This defines how longer is the duration compared to events interval (percentage)
 pref("general.smoothScroll.durationToIntervalRatio", 200);
+// These two prefs determine the timing function.
+pref("general.smoothScroll.currentVelocityWeighting", "0.25");
+pref("general.smoothScroll.stopDecelerationWeighting", "0.4");
 
 pref("profile.confirm_automigration",true);
 // profile.migration_behavior determines how the profiles root is set
 // 0 - use NS_APP_USER_PROFILES_ROOT_DIR
 // 1 - create one based on the NS4.x profile root
 // 2 - use, if not empty, profile.migration_directory otherwise same as 0
 pref("profile.migration_behavior",0);
 pref("profile.migration_directory", "");