Fix CPU profiler crash in start / stop sequence when non-existent name is passed

src/profile-generator-inl.h

 // Copyright 2010 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 79 matching lines @@
 
 void CodeMap::MoveCode(Address from, Address to) {
   tree_.Move(from, to);
 }
 
 void CodeMap::DeleteCode(Address addr) {
   tree_.Remove(addr);
 }
 
 
-bool CpuProfilesCollection::is_last_profile() {
-  // Called from VM thread, and only it can mutate the list,
-  // so no locking is needed here.
-  return current_profiles_.length() == 1;
-}
-
-
 const char* CpuProfilesCollection::GetFunctionName(String* name) {
   return GetFunctionName(GetName(name));
 }
 
 
 const char* CpuProfilesCollection::GetFunctionName(const char* name) {
   return strlen(name) > 0 ? name : ProfileGenerator::kAnonymousFunctionName;
 }
 
 
@@ skipping 11 matching lines @@
       return program_entry_;
     default: return NULL;
   }
 }
 
 } }  // namespace v8::internal
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 #endif  // V8_PROFILE_GENERATOR_INL_H_