Introduce Item flag to selectively activate on stroke-scaling on classes that support it.

Closes #721

src/item/Item.js

@@ -49,6 +49,7 @@ var Item = Base.extend(Emitter, /** @lends Item# */{
     // Exceptions are Raster, PlacedSymbol, Clip and Shape.
     _applyMatrix: true,
     _canApplyMatrix: true,
+    _canScaleStroke: false,
     _boundsSelected: false,
     _selectChildren: false,
     // Provide information about fields to be serialized, with their defaults
@@ -3981,7 +3982,8 @@ var Item = Base.extend(Emitter, /** @lends Item# */{
         var strokeMatrix = parentStrokeMatrix
                 ? parentStrokeMatrix.chain(matrix)
                 // pass `true` for dontMerge
-                : !this.getStrokeScaling(true) && getViewMatrix(globalMatrix),
+                : this._canScaleStroke && !this.getStrokeScaling(true)
+                    && getViewMatrix(globalMatrix),
             // If we're drawing into a separate canvas and a clipItem is defined
             // for the current rendering loop, we need to draw the clip item
             // again.

src/item/Shape.js

@@ -21,6 +21,7 @@ var Shape = Item.extend(/** @lends Shape# */{
     _class: 'Shape',
     _applyMatrix: false,
     _canApplyMatrix: false,
+    _canScaleStroke: true,
     _boundsSelected: true,
     _serializeFields: {
         type: null,

src/path/PathItem.js

@@ -21,6 +21,7 @@
  */
 var PathItem = Item.extend(/** @lends PathItem# */{
     _class: 'PathItem',
+    _canScaleStroke: true,
 
     initialize: function PathItem() {
         // Do nothing.