Add _Merged suffix to merged dartium implementation files.

lib/html/scripts/systemhtml.py

 #!/usr/bin/python
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 """This module provides shared functionality for the system to generate
 Dart:html APIs from the IDL database."""
 
 import emitter
 
@@ skipping 545 matching lines @@
          ID=typename,
          EXTENDS=extends_str)
 
     self._type_comment_emitter.Emit("/// @domName $DOMNAME",
         DOMNAME=self._interface.doc_js_name)
 
     if self._backend.HasImplementation():
       if not self._interface.id in _merged_html_interfaces:
         filename = '%sImpl.dart' % self._html_interface_name
       else:
-        filename = '%sImpl.dart' % self._interface.id
+        filename = '%sImpl_Merged.dart' % self._html_interface_name
       self._implementation_emitter = self._system._CreateEmitter(filename)
     else:
       self._implementation_emitter = emitter.Emitter()
     self._backend.SetImplementationEmitter(self._implementation_emitter)
     self._implementation_members_emitter = self._backend.StartInterface()
 
     for constructor_info in constructors:
       self._members_emitter.Emit(
           '\n'
           '  $CTOR($PARAMS);\n',
@@ skipping 645 matching lines @@
     return HtmlDart2JSClassGenerator(self, interface)
 
   def GenerateLibraries(self, dart_files):
     self._GenerateLibFile(
         'html_dart2js.darttemplate',
         os.path.join(self._output_dir, 'html_dart2js.dart'),
         dart_files)
 
   def Finish(self):
     pass