Introduce ThreadableLoadingContext: make threaded loading code one step away from Document

third_party/WebKit/Source/core/loader/BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//third_party/WebKit/Source/core/core.gni")
 
 blink_core_sources("loader") {
   sources = [
     "CookieJar.cpp",
     "DocumentLoadTiming.cpp",
@@ skipping 29 matching lines @@
     "PingLoader.h",
     "PrerendererClient.cpp",
     "PrerendererClient.h",
     "ProgressTracker.cpp",
     "TextResourceDecoderBuilder.cpp",
     "TextResourceDecoderBuilder.h",
     "TextTrackLoader.cpp",
     "TextTrackLoader.h",
     "ThreadableLoader.cpp",
     "ThreadableLoaderClient.h",
+    "ThreadableLoadingContext.cpp",
+    "ThreadableLoadingContext.h",
     "WorkerThreadableLoader.cpp",
     "WorkerThreadableLoader.h",
     "WorkletScriptLoader.cpp",
     "WorkletScriptLoader.h",
     "appcache/ApplicationCache.cpp",
     "appcache/ApplicationCache.h",
     "appcache/ApplicationCacheHost.cpp",
     "appcache/ApplicationCacheHost.h",
     "modulescript/ModuleScriptFetchRequest.h",
     "modulescript/ModuleScriptLoaderClient.h",
@@ skipping 29 matching lines @@
     "resource/TextResource.h",
     "resource/XSLStyleSheetResource.cpp",
     "resource/XSLStyleSheetResource.h",
   ]
 
   configs += [
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 }