Add --trace-hydrogen-stubs flag (default = false).

src/code-stubs-hydrogen.cc

Index: src/code-stubs-hydrogen.cc
diff --git a/src/code-stubs-hydrogen.cc b/src/code-stubs-hydrogen.cc
index 1b341b526676e2408e9bba360e6f70a3ece7fd3b..7d9a00c14316b4d012339399c4aee4293d1c6b16 100644
--- a/src/code-stubs-hydrogen.cc
+++ b/src/code-stubs-hydrogen.cc
@@ -129,7 +129,7 @@ bool CodeStubGraphBuilderBase::BuildGraph() {
   // Update the static counter each time a new code stub is generated.
   isolate()->counters()->code_stubs()->Increment();
 
-  if (FLAG_trace_hydrogen) {
+  if (FLAG_trace_hydrogen_stubs) {
     const char* name = CodeStub::MajorName(stub()->MajorKey(), false);
     PrintF("-----------------------------------------------------------\n");
     PrintF("Compiling stub %s using hydrogen\n", name);