Make scan-on-scavenge less verbose.

src/heap.h

Index: src/heap.h
===================================================================
--- src/heap.h	(revision 8396)
+++ src/heap.h	(working copy)
@@ -894,14 +894,14 @@
 
   inline void increment_scan_on_scavenge_pages() {
     scan_on_scavenge_pages_++;
-    if (FLAG_trace_gc) {
+    if (FLAG_trace_gc_verbose) {
       PrintF("Scan-on-scavenge pages: %d\n", scan_on_scavenge_pages_);
     }
   }
 
   inline void decrement_scan_on_scavenge_pages() {
     scan_on_scavenge_pages_--;
-    if (FLAG_trace_gc) {
+    if (FLAG_trace_gc_verbose) {
       PrintF("Scan-on-scavenge pages: %d\n", scan_on_scavenge_pages_);
     }
   }