Don't throw exceptions when v8 objects/contexts are missing, and catch

chrome/renderer/extensions/module_system.h

 // Copyright (c) 2012 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 CHROME_RENDERER_EXTENSIONS_MODULE_SYSTEM_H_
 #define CHROME_RENDERER_EXTENSIONS_MODULE_SYSTEM_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 150 matching lines @@
       const std::string&);
   // Base implementation of a LazyFieldGetter which uses |require_fn| to require
   // modules.
   static v8::Handle<v8::Value> LazyFieldGetterInner(
       v8::Local<v8::String> property,
       const v8::AccessorInfo& info,
       RequireFunction require_function);
 
   // Return the named source file stored in the source map.
   // |args[0]| - the name of a source file in source_map_.
-  v8::Handle<v8::Value> GetSource(v8::Handle<v8::String> source_name);
+  v8::Handle<v8::Value> GetSource(const std::string& module_name);
 
   // Return an object that contains the native methods defined by the named
   // NativeHandler.
   // |args[0]| - the name of a native handler object.
   v8::Handle<v8::Value> RequireNativeFromString(const std::string& native_name);
   v8::Handle<v8::Value> RequireNative(const v8::Arguments& args);
 
   // Wraps |source| in a (function(require, requireNative, exports) {...}).
   v8::Handle<v8::String> WrapSource(v8::Handle<v8::String> source);
 
-  // Throws an exception in the calling JS context.
-  v8::Handle<v8::Value> ThrowException(const std::string& message);
-
   // A map from module names to the JS source for that module. GetSource()
   // performs a lookup on this map.
   SourceMap* source_map_;
 
   // A map from native handler names to native handlers.
   NativeHandlerMap native_handler_map_;
 
   // When 0, natives are disabled, otherwise indicates how many callers have
   // pinned natives as enabled.
   int natives_enabled_;
 
   // Called when an exception is thrown but not caught in JS.
   scoped_ptr<ExceptionHandler> exception_handler_;
 
   std::set<std::string> overridden_native_handlers_;
 
   DISALLOW_COPY_AND_ASSIGN(ModuleSystem);
 };
 
 }  // extensions
 
 #endif  // CHROME_RENDERER_EXTENSIONS_MODULE_SYSTEM_H_