Report store buffer overflows to v8 counters.

BUG=
R=jkummerow@chromium.org, mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/17303006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15234 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/store-buffer.cc

@@ -121,6 +121,7 @@ void StoreBuffer::TearDown() {
 
 void StoreBuffer::StoreBufferOverflow(Isolate* isolate) {
   isolate->heap()->store_buffer()->Compact();
+  isolate->counters()->store_buffer_overflows()->Increment();
 }