--- a/gfx/layers/apz/src/AsyncPanZoomController.cpp
+++ b/gfx/layers/apz/src/AsyncPanZoomController.cpp
@@ -333,16 +333,21 @@ typedef GenericFlingAnimation FlingAnima
  * Units: screen pixels (for distance)
  *        screen pixels per millisecond (for velocity)
  *
  * \li\b apz.paint_skipping.enabled
  * When APZ is scrolling and sending repaint requests to the main thread, often
  * the main thread doesn't actually need to do a repaint. This pref allows the
  * main thread to skip doing those repaints in cases where it doesn't need to.
  *
+ * \li\b apz.popups.enabled
+ * Determines whether APZ is used for XUL popup widgets with remote content.
+ * Ideally, this should always be true, but it is currently not well tested, and
+ * has known issues, so needs to be prefable.
+ *
  * \li\b apz.record_checkerboarding
  * Whether or not to record detailed info on checkerboarding events.
  *
  * \li\b apz.test.logging_enabled
  * Enable logging of APZ test data (see bug 961289).
  *
  * \li\b apz.touch_move_tolerance
  * See the description for apz.touch_start_tolerance below. This is a similar

--- a/gfx/thebes/gfxPrefs.h
+++ b/gfx/thebes/gfxPrefs.h
@@ -324,16 +324,17 @@ private:
   DECL_GFX_PREF(Live, "apz.overscroll.min_pan_distance_ratio", APZMinPanDistanceRatio, float, 1.0f);
   DECL_GFX_PREF(Live, "apz.overscroll.spring_friction",        APZOverscrollSpringFriction, float, 0.015f);
   DECL_GFX_PREF(Live, "apz.overscroll.spring_stiffness",       APZOverscrollSpringStiffness, float, 0.001f);
   DECL_GFX_PREF(Live, "apz.overscroll.stop_distance_threshold", APZOverscrollStopDistanceThreshold, float, 5.0f);
   DECL_GFX_PREF(Live, "apz.overscroll.stop_velocity_threshold", APZOverscrollStopVelocityThreshold, float, 0.01f);
   DECL_GFX_PREF(Live, "apz.overscroll.stretch_factor",         APZOverscrollStretchFactor, float, 0.5f);
   DECL_GFX_PREF(Live, "apz.paint_skipping.enabled",            APZPaintSkipping, bool, true);
   DECL_GFX_PREF(Live, "apz.peek_messages.enabled",             APZPeekMessages, bool, true);
+  DECL_GFX_PREF(Live, "apz.popups.enabled",                    APZPopupsEnabled, bool, false);
   DECL_GFX_PREF(Live, "apz.printtree",                         APZPrintTree, bool, false);
   DECL_GFX_PREF(Live, "apz.record_checkerboarding",            APZRecordCheckerboarding, bool, false);
   DECL_GFX_PREF(Live, "apz.test.fails_with_native_injection",  APZTestFailsWithNativeInjection, bool, false);
   DECL_GFX_PREF(Live, "apz.test.logging_enabled",              APZTestLoggingEnabled, bool, false);
   DECL_GFX_PREF(Live, "apz.touch_move_tolerance",              APZTouchMoveTolerance, float, 0.0);
   DECL_GFX_PREF(Live, "apz.touch_start_tolerance",             APZTouchStartTolerance, float, 1.0f/4.5f);
   DECL_GFX_PREF(Live, "apz.velocity_bias",                     APZVelocityBias, float, 0.0f);
   DECL_GFX_PREF(Live, "apz.velocity_relevance_time_ms",        APZVelocityRelevanceTime, uint32_t, 150);

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -712,16 +712,17 @@ pref("apz.overscroll.min_pan_distance_ra
 pref("apz.overscroll.spring_friction", "0.015");
 pref("apz.overscroll.spring_stiffness", "0.0018");
 pref("apz.overscroll.stop_distance_threshold", "5.0");
 pref("apz.overscroll.stop_velocity_threshold", "0.01");
 pref("apz.overscroll.stretch_factor", "0.35");
 pref("apz.paint_skipping.enabled", true);
 // Fetch displayport updates early from the message queue
 pref("apz.peek_messages.enabled", true);
+pref("apz.popups.enabled", false);
 
 // Whether to print the APZC tree for debugging
 pref("apz.printtree", false);
 
 #ifdef NIGHTLY_BUILD
 pref("apz.record_checkerboarding", true);
 #else
 pref("apz.record_checkerboarding", false);

--- a/widget/nsBaseWidget.cpp
+++ b/widget/nsBaseWidget.cpp
@@ -892,17 +892,18 @@ nsBaseWidget::ComputeShouldAccelerate()
 }
 
 bool
 nsBaseWidget::UseAPZ()
 {
   return (gfxPlatform::AsyncPanZoomEnabled() &&
           (WindowType() == eWindowType_toplevel ||
            WindowType() == eWindowType_child ||
-           (WindowType() == eWindowType_popup && HasRemoteContent())));
+           (WindowType() == eWindowType_popup && HasRemoteContent() &&
+            gfxPrefs::APZPopupsEnabled())));
 }
 
 void nsBaseWidget::CreateCompositor()
 {
   LayoutDeviceIntRect rect = GetBounds();
   CreateCompositor(rect.width, rect.height);
 }