Fix canvas test for Chrome 37

tests/html/canvasrenderingcontext2d_test.dart

Index: tests/html/canvasrenderingcontext2d_test.dart
diff --git a/tests/html/canvasrenderingcontext2d_test.dart b/tests/html/canvasrenderingcontext2d_test.dart
index 73eeeb7a2ddd8fc1d09244fc215778811d5b13d2..ffd8b8db6cb0e743ab1064fcef15e51795713121 100644
--- a/tests/html/canvasrenderingcontext2d_test.dart
+++ b/tests/html/canvasrenderingcontext2d_test.dart
@@ -678,7 +678,7 @@ main() {
       // Draw a blue box.
       context.fillText('█', x, y);
 
-      var width = context.measureText('█').width.toInt();
+      var width = context.measureText('█').width.ceil();
 
       checkPixel(readPixel(x, y), [0, 0, 255, 255]);
       checkPixel(readPixel(x + 10, y), [0, 0, 255, 255]);
@@ -699,7 +699,7 @@ main() {
       // Draw a blue box with null maxWidth.
       context.fillText('█', x, y, null);
 
-      var width = context.measureText('█').width.toInt();
+      var width = context.measureText('█').width.ceil();
 
       checkPixel(readPixel(x, y), [0, 0, 255, 255]);
       checkPixel(readPixel(x + 10, y), [0, 0, 255, 255]);