Add operators test to source_mapping_test.

tests/compiler/dart2js/sourcemaps/colors.dart

 // Copyright (c) 2015, 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.
 
 /// Utility library for creating web colors.
 
 library colors;
 
 /// A web color.
 abstract class Color {
-  /// The hexadecimal code for the color, without the prefixed '#'.
-  String get toHex;
+  /// The css code for the color.
+  String get toCss;
 }
 
 /// A web color defined as RGB.
 class RGB implements Color {
   final double r;
   final double g;
   final double b;
 
   /// Creates a color defined by the amount of red [r], green [g], and blue [b]
   /// all in range 0..1.
   const RGB(this.r, this.g, this.b);
 
-  String get toHex {
+  String get toCss {
     StringBuffer sb = new StringBuffer();
+    sb.write('#');
 
     void writeHex(double value) {
       int i = (value * 255.0).round();
       if (i < 16) {
         sb.write('0');
       }
       sb.write(i.toRadixString(16));
     }
 
     writeHex(r);
     writeHex(g);
     writeHex(b);
 
     return sb.toString();
   }
 
   String toString() => 'rgb($r,$g,$b)';
 }
 
+class RGBA extends RGB {
+  final double a;
+
+  const RGBA(double r, double g, double b, this.a) : super(r, g, b);
+
+  String get toCss {
+    StringBuffer sb = new StringBuffer();
+
+    void writeInt(double value) {
+      int i = (value * 255.0).round();
+      if (i < 16) {
+        sb.write('0');
+      }
+      sb.write(i);
+    }
+
+    sb.write('rgba(');
+    writeInt(r);
+    sb.write(', ');
+    writeInt(g);
+    sb.write(', ');
+    writeInt(b);
+    sb.write(', ');
+    sb.write(a);
+    sb.write(')');
+
+    return sb.toString();
+  }
+
+}
+
 /// A web color defined as HSV.
 class HSV implements Color {
   final double h;
   final double s;
   final double v;
 
   /// Creates a color defined by the hue [h] in range 0..360 (360 excluded),
   /// saturation [s] in range 0..1, and value [v] in range 0..1.
   const HSV(this.h, this.s, this.v);
 
-  String get toHex => toRGB(this).toHex;
+  String get toCss => toRGB(this).toCss;
 
   static RGB toRGB(HSV hsv) {
     double h = hsv.h;
     double s = hsv.s;
     double v = hsv.v;
     if (s == 0.0) {
       // Grey.
       return new RGB(v, v, v);
     }
     h /= 60.0;  // Sector 0 to 5.
@@ skipping 13 matching lines @@
         return new RGB(p, q, v);
       case 4:
         return new RGB(t, p, v);
       default:    // case 5:
         return new RGB(v, p, q);
     }
   }
 
   String toString() => 'hsv($h,$s,$v)';
 }