Background parsing: Ensure we don't use the Isolate on a background thread.

src/background-parsing-task.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/background-parsing-task.h"
 #include "src/debug/debug.h"
 
 namespace v8 {
 namespace internal {
 
@@ skipping 31 matching lines @@
   DisallowHandleAllocation no_handles;
   DisallowHandleDereference no_deref;
 
   ScriptData* script_data = NULL;
   ScriptCompiler::CompileOptions options = source_->info->compile_options();
   if (options == ScriptCompiler::kProduceParserCache ||
       options == ScriptCompiler::kProduceCodeCache) {
     source_->info->set_cached_data(&script_data);
   }
 
+  // Nullify the Isolate temporarily so that the background parser doesn't
+  // accidentally use it.
+  Isolate* isolate = source_->info->isolate();
+  source_->info->set_isolate(nullptr);
+
   uintptr_t stack_limit =
       reinterpret_cast<uintptr_t>(&stack_limit) - stack_size_ * KB;
 
   source_->info->set_stack_limit(stack_limit);
   // Parser needs to stay alive for finalizing the parsing on the main
   // thread. Passing &parse_info is OK because Parser doesn't store it.
   source_->parser.reset(new Parser(source_->info.get()));
   source_->parser->ParseOnBackground(source_->info.get());
 
   if (script_data != NULL) {
     source_->cached_data.reset(new ScriptCompiler::CachedData(
         script_data->data(), script_data->length(),
         ScriptCompiler::CachedData::BufferOwned));
     script_data->ReleaseDataOwnership();
     delete script_data;
   }
+  source_->info->set_isolate(isolate);
 }
 }  // namespace internal
 }  // namespace v8