Exposing DOM float & double types as double rather than num.

tools/dom/templates/html/impl/impl_CanvasRenderingContext2D.darttemplate

Index: tools/dom/templates/html/impl/impl_CanvasRenderingContext2D.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_CanvasRenderingContext2D.darttemplate b/tools/dom/templates/html/impl/impl_CanvasRenderingContext2D.darttemplate
index 22b56c2b9ee983e5d309d77eb9e99173eee5b942..3402f7346c12971286fd657e5134f8d255da5828 100644
--- a/tools/dom/templates/html/impl/impl_CanvasRenderingContext2D.darttemplate
+++ b/tools/dom/templates/html/impl/impl_CanvasRenderingContext2D.darttemplate
@@ -95,38 +95,38 @@ $!MEMBERS
 $if DART2JS
     if (sourceRect == null) {
       drawImageScaled(source,
-          destRect.left,
-          destRect.top,
-          destRect.width,
-          destRect.height);
+          destRect.left.toDouble(),
+          destRect.top.toDouble(),
+          destRect.width.toDouble(),
+          destRect.height.toDouble());
     } else {
       drawImageScaledFromSource(source,
-          sourceRect.left,
-          sourceRect.top,
-          sourceRect.width,
-          sourceRect.height,
-          destRect.left,
-          destRect.top,
-          destRect.width,
-          destRect.height);
+          sourceRect.left.toDouble(),
+          sourceRect.top.toDouble(),
+          sourceRect.width.toDouble(),
+          sourceRect.height.toDouble(),
+          destRect.left.toDouble(),
+          destRect.top.toDouble(),
+          destRect.width.toDouble(),
+          destRect.height.toDouble());
     }
 $else
     if (sourceRect == null) {
       _drawImage(source,
-          destRect.left,
-          destRect.top,
-          destRect.width,
-          destRect.height);
+          destRect.left.toDouble(),
+          destRect.top.toDouble(),
+          destRect.width.toDouble(),
+          destRect.height.toDouble());
     } else {
       _drawImage(source,
-          sourceRect.left,
-          sourceRect.top,
-          sourceRect.width,
-          sourceRect.height,
-          destRect.left,
-          destRect.top,
-          destRect.width,
-          destRect.height);
+          sourceRect.left.toDouble(),
+          sourceRect.top.toDouble(),
+          sourceRect.width.toDouble(),
+          sourceRect.height.toDouble(),
+          destRect.left.toDouble(),
+          destRect.top.toDouble(),
+          destRect.width.toDouble(),
+          destRect.height.toDouble());
     }
 $endif
   }