[ES6 modules] ModuleMap::GetFetchedModuleScript to return nullptr when entry not found / "fetching"

third_party/WebKit/Source/core/dom/ModuleMap.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 ModuleMap_h
 #define ModuleMap_h
 
 #include "core/CoreExport.h"
 #include "platform/bindings/ScriptWrappable.h"
 #include "platform/bindings/TraceWrapperMember.h"
@@ skipping 23 matching lines @@
   }
   DECLARE_TRACE();
   DECLARE_TRACE_WRAPPERS();
 
   // https://html.spec.whatwg.org/multipage/webappapis.html#fetch-a-single-module-script
   void FetchSingleModuleScript(const ModuleScriptFetchRequest&,
                                ModuleGraphLevel,
                                SingleModuleClient*);
 
   // Synchronously get the ModuleScript for a given URL.
-  // Note: fetchSingleModuleScript of the ModuleScript must be complete before
-  // calling this.
+  // If the URL wasn't fetched, or is currently being fetched, this returns a
+  // nullptr.
   ModuleScript* GetFetchedModuleScript(const KURL&) const;
 
   Modulator* GetModulator() { return modulator_; }
 
  private:
   explicit ModuleMap(Modulator*);
 
   using MapImpl = HeapHashMap<KURL, TraceWrapperMember<Entry>>;
 
   // A module map is a map of absolute URLs to map entry.
   MapImpl map_;
 
   Member<Modulator> modulator_;
 };
 
 }  // namespace blink
 
 #endif