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

src/compiler.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1229 matching lines @@
   if (FLAG_hydrogen_stats) {
     unsigned size = zone()->allocation_size();
     size += info_->zone()->allocation_size() - info_zone_start_allocation_size_;
     int64_t ticks = OS::Ticks() - start_ticks_;
     isolate()->GetHStatistics()->SaveTiming(name_, ticks, size);
   }
 }
 
 
 bool CompilationPhase::ShouldProduceTraceOutput() const {
-  // Produce trace output if flag is set so that the first letter of the
-  // phase name matches the command line parameter FLAG_trace_phase.
-  return (FLAG_trace_hydrogen &&
-          OS::StrChr(const_cast<char*>(FLAG_trace_phase), name_[0]) != NULL);
+  // Trace if the appropriate trace flag is set and the phase name's first
+  // character is in the FLAG_trace_phase command line parameter.
+  bool tracing_on = info()->IsStub() ?
+      FLAG_trace_hydrogen_stubs :
+      FLAG_trace_hydrogen;
+  return (tracing_on &&
+      OS::StrChr(const_cast<char*>(FLAG_trace_phase), name_[0]) != NULL);
 }
 
 } }  // namespace v8::internal