Do 2 GCs on LowMemoryNotification instead of 7.

src/heap-inl.h

Index: src/heap-inl.h
===================================================================
--- src/heap-inl.h	(revision 12520)
+++ src/heap-inl.h	(working copy)
@@ -774,6 +774,17 @@
 }
 
 
+FlushEagerly::FlushEagerly() {
+  old_state_ = HEAP->flush_eagerly();
+  HEAP->set_flush_eagerly(true);
+}
+
+
+FlushEagerly::~FlushEagerly() {
+  HEAP->set_flush_eagerly(old_state_);
+}
+
+
 #ifdef DEBUG
 AssertNoAllocation::AssertNoAllocation() {
   Isolate* isolate = ISOLATE;