[WIP Prototype] ES6 https://html.spec.whatwg.org/#fetch-a-single-module-script implementation

third_party/WebKit/Source/core/dom/ScriptModuleResolver.h

 // Copyright 2017 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.
 
 #ifndef ScriptModuleResolver_h
 #define ScriptModuleResolver_h
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 #include "platform/wtf/text/WTFString.h"
 
 namespace blink {
 
 class ScriptModule;
 class ModuleScript;
 
 // The ScriptModuleResolver interface is used from V8 module bindings
 // when it need the ScriptModule's descendants.
 //
 // When a module writes import 'x', the module is called the referrer, 'x' is
 // the specifier, and the module identified by 'x' is the descendant.
 // ScriptModuleResolver, given a referrer and specifier, can look up the
 // descendant.
+//
+// In terms of spec, ScriptModuleResolver is also used to set
+// "referencingModule.[[HostDefined]]" used in:
+// https://html.spec.whatwg.org/multipage/webappapis.html#resolve-a-module-specifier
 class CORE_EXPORT ScriptModuleResolver
     : public GarbageCollectedFinalized<ScriptModuleResolver> {
  public:
   virtual ~ScriptModuleResolver() {}
   DEFINE_INLINE_VIRTUAL_TRACE() {}
 
   // Notify the ScriptModuleResolver that a ModuleScript exists.
   // This hook gives a chance for the resolver impl to populate module record
   // identifier -> ModuleScript mapping entry.
   virtual void RegisterModuleScript(ModuleScript*) = 0;
 
   // Implements "Runtime Semantics: HostResolveImportedModule"
   // https://tc39.github.io/ecma262/#sec-hostresolveimportedmodule
   // This returns a null ScriptModule when an exception is thrown.
   virtual ScriptModule Resolve(const String& specifier,
                                const ScriptModule& referrer,
                                ExceptionState&) = 0;
 };
 
 }  // namespace blink
 
 #endif  // ScriptModuleResolver_h