bug 1373583, initialize sActiveIntersliceGCBudget by default to non-zero value, r=jonco

dom/base/nsJSEnvironment.cpp

@@ -195,7 +195,7 @@ static bool sNeedsFullCC = false;
 static bool sNeedsFullGC = false;
 static bool sNeedsGCAfterCC = false;
 static bool sIncrementalCC = false;
-static int32_t sActiveIntersliceGCBudget = 0; // ms;
+static int32_t sActiveIntersliceGCBudget = 5; // ms;
 static nsScriptNameSpaceManager *gNameSpaceManager;
 
 static PRTime sFirstCollectionTime;