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

src/profile-generator.cc

 // 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 524 matching lines @@
                               static_cast<uint32_t>(profile->uid()),
                               true);
     ASSERT(entry->value == NULL);
     entry->value = reinterpret_cast<void*>(unabridged_list->length() - 1);
     return GetProfile(security_token_id, profile->uid());
   }
   return NULL;
 }
 
 
-CpuProfile* CpuProfilesCollection::StopProfiling(int security_token_id,
-                                                 String* title,
-                                                 double actual_sampling_rate) {
-  return StopProfiling(security_token_id, GetName(title), actual_sampling_rate);
-}
-
-
 CpuProfile* CpuProfilesCollection::GetProfile(int security_token_id,
                                               unsigned uid) {
   HashMap::Entry* entry = profiles_uids_.Lookup(reinterpret_cast<void*>(uid),
                                                 static_cast<uint32_t>(uid),
                                                 false);
   int index;
   if (entry != NULL) {
     index = static_cast<int>(reinterpret_cast<intptr_t>(entry->value));
   } else {
     return NULL;
   }
   List<CpuProfile*>* unabridged_list =
       profiles_by_token_[TokenToIndex(TokenEnumerator::kNoSecurityToken)];
   if (security_token_id == TokenEnumerator::kNoSecurityToken) {
     return unabridged_list->at(index);
   }
   List<CpuProfile*>* list = GetProfilesList(security_token_id);
   if (list->at(index) == NULL) {
       list->at(index) =
           unabridged_list->at(index)->FilteredClone(security_token_id);
   }
   return list->at(index);
 }
 
 
+bool CpuProfilesCollection::IsLastProfile(const char* title) {
+  // Called from VM thread, and only it can mutate the list,
+  // so no locking is needed here.
+  if (current_profiles_.length() != 1) return false;
+  return StrLength(title) == 0
+      || strcmp(current_profiles_[0]->title(), title) == 0;
+}
+
+
 int CpuProfilesCollection::TokenToIndex(int security_token_id) {
   ASSERT(TokenEnumerator::kNoSecurityToken == -1);
   return security_token_id + 1;  // kNoSecurityToken -> 0, 0 -> 1, ...
 }
 
 
 List<CpuProfile*>* CpuProfilesCollection::GetProfilesList(
     int security_token_id) {
   const int index = TokenToIndex(security_token_id);
   const int lists_to_add = index - profiles_by_token_.length() + 1;
@@ skipping 1542 matching lines @@
     HeapEntry* entry = added_entries[i];
     if (entry->painted_reachable())
       diff->AddAddedEntry(add_child_index++, added_entry_index++, entry);
   }
   return diff;
 }
 
 } }  // namespace v8::internal
 
 #endif  // ENABLE_LOGGING_AND_PROFILING