[css-round-display] Add title for positioning the element along the path instead of polar positioning

Author: Jihye Hong

css-round-display/Overview.bs

@@ -391,37 +391,10 @@ The example below shows how the 'border-boundary' property works on drawing bord
 <p class="note">Note: If the value of 'border-boundary' is parent or display, border lines of the element are actually just a visual effect. It triggers a layout for rendering in a general way, but in the above cases (border-boundary: parent|display), the layout doesn't occur and it only draws the border lines inward from the containing block's borders. With this situation, the borders might hide contents around the display edge.
 </p>
 
-<h2 id="positioning-content">Content positioning using polar coordinate system</h2>
+<h2 id="positioning-content">Position the element along the path</h2>
+This section introduces specifying a path and positioning the element along it.
 
-<p>
-Polar coordinate system is a two-dimensional coordinate system that describes the position of a point in a plane with a distance from a reference point and an angle from a reference direction. Elements could be placed along a circle or concentric circles, and the polar coordinate system is useful to handle such cases.
-
-This section introduces polar positioning to support layout of elements in the polar coordinate system where the position of an element is determined by a distance from the center point within the containing element and an angle from the Y-axis.
-
-The conventional coordinates used in web is the Cartesian coordinate system, but using 'polar-distance' or 'polar-angle' enables positioning an element in the polar coordinate system. The 'polar-angle' and 'polar-distance' properties specify the angular value and distance of an element from the origin in polar coordinates.
-
-</p>
-
-<div class='example'>
-This example shows a way to align elements within the polar coordinate system.
-<pre>&lt;body>
-
-  &lt;div id="circle1" style="position: absolute; polar-angle: 0deg; polar-distance: 50%">&lt;/div>
-  &lt;div id="circle2" style="position: absolute; polar-angle: 90deg; polar-distance: 20%">&lt;/div>
-  &lt;div id="circle3" style="position: absolute; polar-angle: 225deg; polar-distance: 100%">&lt;/div>
-&lt;/body>
-</pre>
-<div style="width: 400px; text-align: center">
-	<img alt="An image of three elements positioned to polar coordinates" src="images/polar_a.png" style="width: 200px; border: 1px #AAA solid; text-align: center"/>
-	<p class="caption">An example of polar positioning</p>
-</div>
-</div>
-
-<p>
-In conventional coordinate system used for positioning an element in a containing block, the offset of the element is applied depending on the edges of the element’s containing block.
-
-In comparison, the default origin of polar coordinates is positioned at the center point of a containing block. The position for the origin point can be set by 'polar-origin'.
-</p>
+A path can be defined with 'offset-path' and 'offset-origin'. The position of the element on the path is computed by the value of 'offset-distance' and 'offset-anchor'.
 
 <h3 id="offset-path-property">Define the path: The 'offset-path' property</h3>