Get rid of System classes for backend generators.

lib/html/scripts/systemhtml.py

Index: lib/html/scripts/systemhtml.py
diff --git a/lib/html/scripts/systemhtml.py b/lib/html/scripts/systemhtml.py
index 10f74623ac14e00be4fca5f6b7e28e91ee023a46..bdf2980f93caaa744a37940db90ac56c0bec6ae8 100644
--- a/lib/html/scripts/systemhtml.py
+++ b/lib/html/scripts/systemhtml.py
@@ -438,26 +438,16 @@ class HtmlSystemShared(object):
 
 
 class HtmlInterfacesSystem(System):
-  def __init__(self, options, dart_library_generator, backend):
+  def __init__(self, options, dart_library_generator, backend_factory):
     super(HtmlInterfacesSystem, self).__init__(options)
     self._dart_library_generator = dart_library_generator
-    self._backend = backend
+    self._backend_factory = backend_factory
     self._shared = HtmlSystemShared(options)
-    self._dart_file_paths = []
     self._elements_factory_emitter = None
 
   def ProcessInterface(self, interface):
-    HtmlDartInterfaceGenerator(self, interface).Generate()
-
-  def ProcessCallback(self, interface, info):
-    """Generates a typedef for the callback interface."""
-    code = self._CreateEmitter('%s.dart' % interface.id)
-    code.Emit(self._templates.Load('callback.darttemplate'))
-    code.Emit('typedef $TYPE $NAME($PARAMS);\n',
-              NAME=interface.id,
-              TYPE=DartType(info.type_name),
-              PARAMS=info.ParametersImplementationDeclaration(DartType))
-    self._backend.ProcessCallback(interface, info)
+    backend = self._backend_factory(interface)
+    HtmlDartInterfaceGenerator(self, interface, backend).Generate()
 
   def _CreateEmitter(self, filename):
     return self._dart_library_generator.CreateFileEmitter(filename)
@@ -467,13 +457,23 @@ class HtmlInterfacesSystem(System):
 class HtmlDartInterfaceGenerator(BaseGenerator):
   """Generates dart interface and implementation for the DOM IDL interface."""
 
-  def __init__(self, system, interface):
+  def __init__(self, system, interface, backend):
     super(HtmlDartInterfaceGenerator, self).__init__(
-        system._database, interface)
+        system._database, system._type_registry, interface)
     self._system = system
+    self._backend = backend
     self._shared = system._shared
     self._html_interface_name = system._renamer.RenameInterface(self._interface)
-    self._backend = system._backend.ImplementationGenerator(self._interface)
+
+  def GenerateCallback(self, info):
+    """Generates a typedef for the callback interface."""
+    code = self._system._CreateEmitter('%s.dart' % self._interface.id)
+    code.Emit(self._system._templates.Load('callback.darttemplate'))
+    code.Emit('typedef $TYPE $NAME($PARAMS);\n',
+              NAME=self._interface.id,
+              TYPE=DartType(info.type_name),
+              PARAMS=info.ParametersImplementationDeclaration(DartType))
+    self._backend.GenerateCallback(info)
 
   def StartInterface(self):
     if not self._interface.id in _merged_html_interfaces:
@@ -760,15 +760,14 @@ class HtmlGeneratorDummyBackend(object):
 
 # TODO(jmesserly): inheritance is probably not the right way to factor this long
 # term, but it makes merging better for now.
-class HtmlDart2JSClassGenerator(Dart2JSInterfaceGenerator):
+class Dart2JSBackend(Dart2JSInterfaceGenerator):
   """Generates a dart2js class for the dart:html library from a DOM IDL
   interface.
   """
 
-  def __init__(self, system, interface):
-    super(HtmlDart2JSClassGenerator, self).__init__(
-        system, interface, None, None)
-    self._html_interface_name = system._renamer.RenameInterface(self._interface)
+  def __init__(self, interface, options):
+    super(Dart2JSBackend, self).__init__(options, interface, None, None)
+    self._html_interface_name = options.renamer.RenameInterface(self._interface)
 
   def HasImplementation(self):
     return not (IsPureInterface(self._interface.id) or
@@ -817,8 +816,8 @@ class HtmlDart2JSClassGenerator(Dart2JSInterfaceGenerator):
       implements.append('JavaScriptIndexingBehavior')
 
     template_file = 'impl_%s.darttemplate' % self._html_interface_name
-    template = (self._system._templates.TryLoad(template_file) or
-                self._system._templates.Load('dart2js_impl.darttemplate'))
+    template = (self._template_loader.TryLoad(template_file) or
+                self._template_loader.Load('dart2js_impl.darttemplate'))
     self._members_emitter = self._dart_code.Emit(
         template,
         #class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
@@ -837,9 +836,9 @@ class HtmlDart2JSClassGenerator(Dart2JSInterfaceGenerator):
   def EmitFactoryProvider(self, constructor_info, factory_provider, emitter):
     template_file = ('factoryprovider_%s.darttemplate' %
                      self._html_interface_name)
-    template = self._system._templates.TryLoad(template_file)
+    template = self._template_loader.TryLoad(template_file)
     if not template:
-      template = self._system._templates.Load('factoryprovider.darttemplate')
+      template = self._template_loader.Load('factoryprovider.darttemplate')
 
     emitter.Emit(
         template,
@@ -894,7 +893,7 @@ class HtmlDart2JSClassGenerator(Dart2JSInterfaceGenerator):
     # TODO(sra): Use separate mixins for typed array implementations of List<T>.
     if self._interface.id != 'NodeList':
       template_file = 'immutable_list_mixin.darttemplate'
-      template = self._system._templates.Load(template_file)
+      template = self._template_loader.Load(template_file)
       self._members_emitter.Emit(template, E=self._DartType(element_type))
 
   def AddAttribute(self, attribute, html_name, read_only):
@@ -1217,16 +1216,8 @@ class HtmlDart2JSClassGenerator(Dart2JSInterfaceGenerator):
     if element_type and requires_indexer: return True
     return False
 
-# ------------------------------------------------------------------------------
-
-class HtmlDart2JSSystem(System):
-
-  def __init__(self, options):
-    super(HtmlDart2JSSystem, self).__init__(options)
-
-  def ImplementationGenerator(self, interface):
-    return HtmlDart2JSClassGenerator(self, interface)
 
+# ------------------------------------------------------------------------------
 
 class DartLibraryEmitter():
   def __init__(self, emitters, template, dart_sources_dir):