--- a/gfx/layers/apz/src/APZCTreeManager.cpp
+++ b/gfx/layers/apz/src/APZCTreeManager.cpp
@@ -1412,17 +1412,18 @@ APZCTreeManager::ProcessTouchInput(Multi
 
     mHitResultForInputBlock = HitNothing;
     mApzcForInputBlock = GetTouchInputBlockAPZC(aInput, &touchBehaviors,
         &mHitResultForInputBlock, &hitScrollbarNode);
 
     // Check if this event starts a scrollbar touch-drag. The conditions
     // checked are similar to the ones we check for MOUSE_INPUT starting
     // a scrollbar mouse-drag.
-    mInScrollbarTouchDrag = gfxPrefs::APZDragEnabled() && hitScrollbarNode &&
+    mInScrollbarTouchDrag = gfxPrefs::APZDragEnabled() &&
+                            gfxPrefs::APZTouchDragEnabled() && hitScrollbarNode &&
                             hitScrollbarNode->IsScrollThumbNode() &&
                             hitScrollbarNode->GetScrollThumbData().mIsAsyncDraggable;
 
     MOZ_ASSERT(touchBehaviors.Length() == aInput.mTouches.Length());
     for (size_t i = 0; i < touchBehaviors.Length(); i++) {
       APZCTM_LOG("Touch point has allowed behaviours 0x%02x\n", touchBehaviors[i]);
       if (touchBehaviors[i] == AllowedTouchBehavior::UNKNOWN) {
         // If there's any unknown items in the list, throw it out and we'll

--- a/gfx/layers/apz/src/AsyncPanZoomController.cpp
+++ b/gfx/layers/apz/src/AsyncPanZoomController.cpp
@@ -194,16 +194,29 @@ typedef GenericFlingAnimation FlingAnima
  * \li\b apz.displayport_expiry_ms
  * While a scrollable frame is scrolling async, we set a displayport on it
  * to make sure it is layerized. However this takes up memory, so once the
  * scrolling stops we want to remove the displayport. This pref controls how
  * long after scrolling stops the displayport is removed. A value of 0 will
  * disable the expiry behavior entirely.
  * Units: milliseconds
  *
+ * \li\b apz.drag.enabled
+ * Setting this pref to true will cause APZ to handle mouse-dragging of
+ * scrollbar thumbs.
+ *
+ * \li\b apz.drag.initial.enabled
+ * Setting this pref to true will cause APZ to try to handle mouse-dragging
+ * of scrollbar thumbs without an initial round-trip to content to start it
+ * if possible. Only has an effect if apz.drag.enabled is also true.
+ *
+ * \li\b apz.drag.touch.enabled
+ * Setting this pref to true will cause APZ to handle touch-dragging of
+ * scrollbar thumbs. Only has an effect if apz.drag.enabled is also true.
+ *
  * \li\b apz.enlarge_displayport_when_clipped
  * Pref that enables enlarging of the displayport along one axis when the
  * generated displayport's size is beyond that of the scrollable rect on the
  * opposite axis.
  *
  * \li\b apz.fling_accel_interval_ms
  * The time that determines whether a second fling will be treated as
  * accelerated. If two flings are started within this interval, the second one

--- a/gfx/thebes/gfxPrefs.h
+++ b/gfx/thebes/gfxPrefs.h
@@ -293,16 +293,17 @@ private:
   DECL_GFX_PREF(Live, "apz.axis_lock.mode",                    APZAxisLockMode, int32_t, 0);
   DECL_GFX_PREF(Live, "apz.content_response_timeout",          APZContentResponseTimeout, int32_t, 400);
   DECL_GFX_PREF(Live, "apz.danger_zone_x",                     APZDangerZoneX, int32_t, 50);
   DECL_GFX_PREF(Live, "apz.danger_zone_y",                     APZDangerZoneY, int32_t, 100);
   DECL_GFX_PREF(Live, "apz.disable_for_scroll_linked_effects", APZDisableForScrollLinkedEffects, bool, false);
   DECL_GFX_PREF(Live, "apz.displayport_expiry_ms",             APZDisplayPortExpiryTime, uint32_t, 15000);
   DECL_GFX_PREF(Live, "apz.drag.enabled",                      APZDragEnabled, bool, false);
   DECL_GFX_PREF(Live, "apz.drag.initial.enabled",              APZDragInitiationEnabled, bool, false);
+  DECL_GFX_PREF(Live, "apz.drag.touch.enabled",                APZTouchDragEnabled, bool, false);
   DECL_GFX_PREF(Live, "apz.enlarge_displayport_when_clipped",  APZEnlargeDisplayPortWhenClipped, bool, false);
   DECL_GFX_PREF(Live, "apz.fling_accel_base_mult",             APZFlingAccelBaseMultiplier, float, 1.0f);
   DECL_GFX_PREF(Live, "apz.fling_accel_interval_ms",           APZFlingAccelInterval, int32_t, 500);
   DECL_GFX_PREF(Live, "apz.fling_accel_supplemental_mult",     APZFlingAccelSupplementalMultiplier, float, 1.0f);
   DECL_GFX_PREF(Live, "apz.fling_accel_min_velocity",          APZFlingAccelMinVelocity, float, 1.5f);
   DECL_GFX_PREF(Once, "apz.fling_curve_function_x1",           APZCurveFunctionX1, float, 0.0f);
   DECL_GFX_PREF(Once, "apz.fling_curve_function_x2",           APZCurveFunctionX2, float, 1.0f);
   DECL_GFX_PREF(Once, "apz.fling_curve_function_y1",           APZCurveFunctionY1, float, 0.0f);

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -668,16 +668,17 @@ pref("apz.autoscroll.enabled", true);
 pref("apz.axis_lock.mode", 0);
 pref("apz.axis_lock.lock_angle", "0.5235987");        // PI / 6 (30 degrees)
 pref("apz.axis_lock.breakout_threshold", "0.03125");  // 1/32 inches
 pref("apz.axis_lock.breakout_angle", "0.3926991");    // PI / 8 (22.5 degrees)
 pref("apz.axis_lock.direct_pan_angle", "1.047197");   // PI / 3 (60 degrees)
 pref("apz.content_response_timeout", 400);
 pref("apz.drag.enabled", true);
 pref("apz.drag.initial.enabled", true);
+pref("apz.drag.touch.enabled", true);
 pref("apz.danger_zone_x", 50);
 pref("apz.danger_zone_y", 100);
 pref("apz.disable_for_scroll_linked_effects", false);
 pref("apz.displayport_expiry_ms", 15000);
 pref("apz.enlarge_displayport_when_clipped", false);
 pref("apz.fling_accel_base_mult", "1.0");
 pref("apz.fling_accel_interval_ms", 500);
 pref("apz.fling_accel_min_velocity", "1.5");