Make ModuleSystem have a const view of ResourceBundleSourceMap.

extensions/renderer/module_system_test.cc

 // Copyright 2014 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.
 
 #include "extensions/renderer/module_system_test.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <string>
@@ skipping 87 matching lines @@
 };
 
 // Source map that operates on std::strings.
 class ModuleSystemTestEnvironment::StringSourceMap
     : public ModuleSystem::SourceMap {
  public:
   StringSourceMap() {}
   ~StringSourceMap() override {}
 
   v8::Local<v8::Value> GetSource(v8::Isolate* isolate,
-                                 const std::string& name) override {
+                                 const std::string& name) const override {
     if (source_map_.count(name) == 0)

[Devlin, 2016/04/12 17:01:25]

Unrelated to this patch, but this is a double look-up.  Can we make this just
use find() from the start?

[lazyboy, 2016/04/12 17:29:28]

Good catch, thank you.
Done.

       return v8::Undefined(isolate);
-    return v8::String::NewFromUtf8(isolate, source_map_[name].c_str());
+    return v8::String::NewFromUtf8(isolate,
+                                   source_map_.find(name)->second.c_str());
   }
 
-  bool Contains(const std::string& name) override {
+  bool Contains(const std::string& name) const override {
     return source_map_.count(name);
   }
 
   void RegisterModule(const std::string& name, const std::string& source) {
     CHECK_EQ(0u, source_map_.count(name)) << "Module " << name << " not found";
     source_map_[name] = source;
   }
 
  private:
   std::map<std::string, std::string> source_map_;
@@ skipping 125 matching lines @@
 
 void ModuleSystemTest::ExpectNoAssertionsMade() {
   should_assertions_be_made_ = false;
 }
 
 void ModuleSystemTest::RunResolvedPromises() {
   v8::MicrotasksScope::PerformCheckpoint(isolate_);
 }
 
 }  // namespace extensions