Fix RenderParagraph to respect text color.

I don't think this is the final API we're going to use.

I suspect we'll add a TextStyle struct to hold
color and size, etc. which back-ends into CSS like
this does today.

Currently no one uses this color even though it exists.

This is one step towards fixing:
https://github.com/domokit/mojo/issues/213

R=ianh@google.com

Review URL: https://codereview.chromium.org/1162573007

engine/core/painting/Color.dart

@@ -15,6 +15,11 @@ class Color {
               ((g & 0xff) << 8) |
               ((b & 0xff) << 0));
 
+  int get alpha => (0xff000000 & _value) >> 24;
+  int get red => (0x00ff0000 & _value) >> 16;
+  int get green => (0x0000ff00 & _value) >> 8;
+  int get blue => (0x000000ff & _value) >> 0;
+
   bool operator ==(other) => other is Color && _value == other._value;
 
   int get hashCode => _value.hashCode;

sdk/lib/framework/rendering/paragraph.dart

@@ -76,7 +76,9 @@ class RenderParagraph extends RenderBox {
   }
 
   void paint(RenderObjectDisplayList canvas) {
-    // _layoutRoot.rootElement.style['color'] = 'rgba(' + ...color... + ')';
+    if (_color != null)
+      _layoutRoot.rootElement.style['color'] =
+          'rgba(${_color.red}, ${_color.green}, ${_color.blue}, ${_color.alpha / 255.0 })';
     _layoutRoot.paint(canvas);
   }
 

tests/framework/color_accessors-expected.txt

+CONSOLE: unittest-suite-wait-for-done
+CONSOLE: PASS: color accessors should work
+CONSOLE: 
+CONSOLE: All 1 tests passed.
+CONSOLE: unittest-suite-success
+DONE

tests/framework/color_accessors.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 'dart:sky';
+import '../resources/third_party/unittest/unittest.dart';
+import '../resources/unit.dart';
+
+void main() {
+  initUnit();
+
+  test("color accessors should work", () {
+    Color foo = new Color(0x12345678);
+    expect(foo.alpha, equals(0x12));
+    expect(foo.red, equals(0x34));
+    expect(foo.green, equals(0x56));
+    expect(foo.blue, equals(0x78));
+  });
+}