Expand the grid size of the Multiply test automatically when needed

#52

Enlarge the grid size and reduce the tile size when a larger complexity is needed
to lower the frame rate.

Refactor the spiral iterator into a separate class. Keep calling its next() method
to move to the next cell. When its isDone() returns true enlarge the iterator grid
size and resize the already created tiles to fit in the new grid size.

Add a new class for the roundedRect tile called "Tile". This class can handle the
location, size and animation of the Tile.

MotionMark/resources/extensions.js

@@ -265,18 +265,41 @@ Point = Utilities.createClass(
         return this.x;
     },
 
+    // Used when the point object is used as a size object.
+    set width(w)
+    {
+        this.x = w;
+    },
+
     // Used when the point object is used as a size object.
     get height()
     {
         return this.y;
     },
 
+    // Used when the point object is used as a size object.
+    set height(h)
+    {
+        this.y = h;
+    },
+
     // Used when the point object is used as a size object.
     get center()
     {
         return new Point(this.x / 2, this.y / 2);
     },
 
+    // Used when the point object is used as a size object.
+    area: function() {
+        return this.x * this.y;
+    },
+
+    // Used when the point object is used as a size object.
+    expand(width, height) {
+        this.x += width;
+        this.y += height;
+    },
+
     str: function()
     {
         return "x = " + this.x + ", y = " + this.y;
@@ -320,6 +343,9 @@ Point = Utilities.createClass(
     }
 });
 
+// FIXME: Add a seprate class for Size.
+let Size = Point;
+
 Utilities.extendObject(Point, {
     zero: new Point(0, 0),