Bug 1302523 - Don't start incremental GCs if they have been disabled, r=sfink.

--HG--
extra : rebase_source : bea0b930a6c908b4ad5c5dfdb22fab108bbb4dff

js/src/jsgc.cpp

@@ -6355,6 +6355,10 @@ void
 GCRuntime::startGC(JSGCInvocationKind gckind, JS::gcreason::Reason reason, int64_t millis)
 {
     MOZ_ASSERT(!isIncrementalGCInProgress());
+    if (!JS::IsIncrementalGCEnabled(rt->contextFromMainThread())) {
+        gc(gckind, reason);
+        return;
+    }
     invocationKind = gckind;
     collect(false, defaultBudget(reason, millis), reason);
 }