Backed out changesets 4f35e943f939 and da5fa63e90cb (bug 896250) for causing frequent OSX debug asserts on a CLOSED TREE.

layout/base/nsDisplayList.cpp

@@ -1500,7 +1500,7 @@ nsDisplayItem::ForceActiveLayers()
 /* static */ int32_t
 nsDisplayItem::MaxActiveLayers()
 {
-  static int32_t sMaxLayers = -1;
+  static int32_t sMaxLayers = false;
   static bool sMaxLayersCached = false;
 
   if (!sMaxLayersCached) {
@@ -1508,7 +1508,7 @@ nsDisplayItem::MaxActiveLayers()
     sMaxLayersCached = true;
   }
 
-  return sMaxLayers;
+  return sMaxLayersCached;
 }
 
 bool

mobile/android/app/mobile.js

@@ -551,7 +551,7 @@ pref("layers.low-precision-resolution", 250);
 // 2) Pages that have too many layers consume too much memory and crash.
 // By limiting the number of layers on mobile we're making the main thread
 // work harder keep scrolling smooth and memory low.
-pref("layers.max-active", 1);
+pref("layers.max-active", 20);
 
 pref("notification.feature.enabled", true);
 pref("dom.webnotifications.enabled", true);