Refactoring to support dark theme better

sky/sdk/lib/editing/input.dart

 // Copyright 2015 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.
 
 import '../painting/text_style.dart';
 import '../widgets/basic.dart';
 import '../widgets/theme.dart';
 import 'editable_string.dart';
 import 'editable_text.dart';
 import 'keyboard.dart';
@@ skipping 50 matching lines @@
 
     if (placeholder != null && _value.isEmpty) {
       Widget child = new Opacity(
         key: "placeholder",
         child: new Text(placeholder, style: textStyle),
         opacity: _kHintOpacity
       );
       textChildren.add(child);
     }
 
+    ThemeData themeData = Theme.of(this);
+    Color focusHighlightColor = themeData.accentColor;
+    Color cursorColor = themeData.accentColor;
+    if (themeData.primarySwatch != null) {
+      cursorColor = Theme.of(this).primarySwatch[200];
+      focusHighlightColor = focused ? themeData.primarySwatch[400] : themeData.primarySwatch[200];
+    }
+
     textChildren.add(new EditableText(
       value: _editableValue, 
       focused: focused,
       style: textStyle,
-      cursorColor: Theme.of(this).primary[200]
+      cursorColor: cursorColor
     ));
 
     Border focusHighlight = new Border(bottom: new BorderSide(
-      color: focused ? Theme.of(this).primary[400] : Theme.of(this).primary[200],
+      color: focusHighlightColor,
       width: focused ? 2.0 : 1.0
     ));
 
     Container input = new Container(
       child: new Stack(textChildren),
       padding: _kTextfieldPadding,
       decoration: new BoxDecoration(border: focusHighlight)
     );
 
     return new Listener(
       child: input,
       onPointerDown: (_) => keyboard.showByRequest()
     );
   }
 
   void didUnmount() {
     if (_isAttachedToKeyboard)
       keyboard.hide();
     super.didUnmount();
   }
 }