Add timestamp to --trace-gc output.

src/isolate.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 1816 matching lines @@
 
   // If we are deserializing, log non-function code objects and compiled
   // functions found in the snapshot.
   if (des != NULL && (FLAG_log_code || FLAG_ll_prof)) {
     HandleScope scope;
     LOG(this, LogCodeObjects());
     LOG(this, LogCompiledFunctions());
   }
 
   state_ = INITIALIZED;
+  time_millis_at_init_ = OS::TimeCurrentMillis();
   return true;
 }
 
 
 // Initialized lazily to allow early
 // v8::V8::SetAddHistogramSampleFunction calls.
 StatsTable* Isolate::stats_table() {
   if (stats_table_ == NULL) {
     stats_table_ = new StatsTable;
   }
@@ skipping 72 matching lines @@
 
 #ifdef DEBUG
 #define ISOLATE_FIELD_OFFSET(type, name, ignored)                       \
 const intptr_t Isolate::name##_debug_offset_ = OFFSET_OF(Isolate, name##_);
 ISOLATE_INIT_LIST(ISOLATE_FIELD_OFFSET)
 ISOLATE_INIT_ARRAY_LIST(ISOLATE_FIELD_OFFSET)
 #undef ISOLATE_FIELD_OFFSET
 #endif
 
 } }  // namespace v8::internal