Adjust small heap threshold for idle time handler.

src/heap/gc-idle-time-handler.h

Index: src/heap/gc-idle-time-handler.h
diff --git a/src/heap/gc-idle-time-handler.h b/src/heap/gc-idle-time-handler.h
index 473b4742d496d3d1baa5e69d1e12115d620630cb..daab616d61b76eb460e0673b91d2b2e60d733178 100644
--- a/src/heap/gc-idle-time-handler.h
+++ b/src/heap/gc-idle-time-handler.h
@@ -108,7 +108,7 @@ class GCIdleTimeHandler {
 
   // Heap size threshold below which we prefer mark-compact over incremental
   // step.
-  static const size_t kSmallHeapSize = 2 * kPointerSize * MB;
+  static const size_t kSmallHeapSize = 4 * kPointerSize * MB;
 
   // That is the maximum idle time we will have during frame rendering.
   static const size_t kMaxFrameRenderingIdleTime = 16;