Fix the release build.

R=ppi@chromium.org

Review URL: https://codereview.chromium.org/1378373002 .
diff --git a/apps/benchmark/event.cc b/apps/benchmark/event.cc
index bdaff1d..49b6a70 100644
--- a/apps/benchmark/event.cc
+++ b/apps/benchmark/event.cc
@@ -55,7 +55,7 @@
   }
 
   if (value->IsType(base::Value::TYPE_INTEGER)) {
-    int id_int;
+    int id_int = 0;
     // We already verified the type, so it should be an integer.
     DCHECK(value->GetAsInteger(&id_int));
     *output = base::IntToString(id_int);