Implement ColorFilter in widgets/basic.dart

Also, trim the redundant |Mode| suffix from the TransferMode names.

R=ianh@google.com

Review URL: https://codereview.chromium.org/1188003006.

examples/game/lib/game_demo_world.dart

@@ -269,7 +269,7 @@ class Laser extends Sprite {
     size = new Size(20.0, 20.0);
     position = ship.position;
     rotation = ship.rotation + 90.0;
-    transferMode = TransferMode.plusMode;
+    transferMode = TransferMode.plus;
     double rotRadians = convertDegrees2Radians(rotation);
     _movementVector = pointMult(new Point(Math.sin(rotRadians), -Math.cos(rotRadians)), 10.0);
     _movementVector = new Point(_movementVector.x + ship._movementVector[0], _movementVector.y + ship._movementVector[1]);
@@ -305,7 +305,7 @@ class StarField extends Node {
   void paint(PictureRecorder canvas) {
     // Setup paint object for opacity and transfer mode
     Paint paint = new Paint();
-    paint.setTransferMode(TransferMode.plusMode);
+    paint.setTransferMode(TransferMode.plus);
 
     double baseScaleX = 32.0/_img.width;
     double baseScaleY = 32.0/_img.height;

examples/game/lib/sprite.dart

@@ -55,7 +55,7 @@ class Sprite extends NodeWithSize {
       Paint paint = new Paint();
       paint.color = new Color.fromARGB((255.0*_opacity).toInt(), 255, 255, 255);
       if (colorOverlay != null) {
-        paint.setColorFilter(new ColorFilter.mode(colorOverlay, TransferMode.srcATopMode));
+        paint.setColorFilter(new ColorFilter.mode(colorOverlay, TransferMode.srcATop));
       }
       if (transferMode != null) {
         paint.setTransferMode(transferMode);

examples/raw/shadow.dart

@@ -17,7 +17,7 @@ void beginFrame(double timeStamp) {
         new DrawLooperLayerInfo()
           ..setPaintBits(PaintBits.all)
           ..setOffset(const Point(5.0, 5.0))
-          ..setColorMode(TransferMode.srcInMode),
+          ..setColorMode(TransferMode.srcIn),
         (Paint layerPaint) {
       layerPaint.color = const Color.fromARGB(128, 55, 55, 55);
       layerPaint.setMaskFilter(