Add counters for write barriers in optimized code.

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index 16b8bd79fb9166b59167a5a50fadd358bef5d77c..fefd70ee0a49d0677cf8a568e2bfb315667ba38c 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -589,6 +589,10 @@ void MacroAssembler::RecordWriteForMap(
     return;
   }
 
+  // Count number of write barriers in generated code.
+  isolate()->counters()->write_barriers_static()->Increment();
+  IncrementCounter(isolate()->counters()->write_barriers_dynamic(), 1);
+
   // A single check of the map's pages interesting flag suffices, since it is
   // only set during incremental collection, and then it's also guaranteed that
   // the from object's page's interesting flag is also set.  This optimization
@@ -645,6 +649,10 @@ void MacroAssembler::RecordWrite(Register object,
     bind(&ok);
   }
 
+  // Count number of write barriers in generated code.
+  isolate()->counters()->write_barriers_static()->Increment();
+  IncrementCounter(isolate()->counters()->write_barriers_dynamic(), 1);
+
   // First, check if a write barrier is even needed. The tests below
   // catch stores of Smis and stores into young gen.
   Label done;