Use loading tq instead of timer tq for per-isolate tasks

third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 376 matching lines @@
 
   DEFINE_STATIC_LOCAL(ArrayBufferAllocator, arrayBufferAllocator, ());
   auto v8ExtrasMode = RuntimeEnabledFeatures::experimentalV8ExtrasEnabled()
                           ? gin::IsolateHolder::kStableAndExperimentalV8Extras
                           : gin::IsolateHolder::kStableV8Extras;
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kNonStrictMode,
                                  v8ExtrasMode, &arrayBufferAllocator);
 
   // NOTE: Some threads (namely utility threads) don't have a scheduler.
   WebScheduler* scheduler = Platform::current()->currentThread()->scheduler();
+  // TODO(altimin): Consider switching to timerTaskRunner here.

[haraken, 2017/01/18 00:05:03]

Add a comment and mention that we use a loading tq to prevent GC tasks from
being throttled.

   v8::Isolate* isolate = V8PerIsolateData::initialize(
-      scheduler ? scheduler->timerTaskRunner()
+      scheduler ? scheduler->loadingTaskRunner()

[haraken, 2017/01/18 00:05:03]

Maybe do we want to use an unthrottled task runner?

[altimin, 2017/01/18 13:07:09]

Most probably we need to expose different task runners to isolate and route
appropriate tasks to appropriate queues.

                 : Platform::current()->currentThread()->getWebTaskRunner());
 
   initializeV8Common(isolate);
 
   isolate->SetOOMErrorHandler(reportOOMErrorInMainThread);
   isolate->SetFatalErrorHandler(reportFatalErrorInMainThread);
   isolate->AddMessageListenerWithErrorLevel(
       messageHandlerInMainThread,
       v8::Isolate::kMessageError | v8::Isolate::kMessageWarning |
           v8::Isolate::kMessageInfo | v8::Isolate::kMessageDebug |
@@ skipping 109 matching lines @@
           v8::Isolate::kMessageLog);
   isolate->SetFatalErrorHandler(reportFatalErrorInWorker);
 
   uint32_t here;
   isolate->SetStackLimit(reinterpret_cast<uintptr_t>(&here) -
                          kWorkerMaxStackSize);
   isolate->SetPromiseRejectCallback(promiseRejectHandlerInWorker);
 }
 
 }  // namespace blink