Fixes #39. Clarify -webkit-background-clip and root element.

compatibility.bs

@@ -87,6 +87,9 @@ urlPrefix: https://encoding.spec.whatwg.org/
 urlPrefix: https://drafts.csswg.org/css-cascade-3/
   type: dfn
     text: important; url: #important
+urlPrefix: https://drafts.csswg.org/css-backgrounds-3/
+  type: dfn
+    text: the backgrounds of special elements;url: #special-backgrounds
 </pre>
 
 <pre class=link-defaults>
@@ -537,7 +540,7 @@ The following <code>-webkit-</code> <a>vendor prefixed</a> keywords must be supp
 Name: -webkit-background-clip
 Value: text
 Initial: none
-Applies to: all elements (Maybe? See <a href="https://github.com/whatwg/compat/issues/39">Issue #39</a>)
+Applies to: all elements
 Inherited: yes
 Computed value: "text"
 Percentages: N/A
@@ -547,6 +550,15 @@ Animatable: no
 
 The <code>'-webkit-background-clip'</code> property causes the background image to clip to foreground text (including decorations and shadows). The shape of the foreground content (including alpha transparency in the content) is applied as a mask to clip background drawing for the box.
 
+<div class="note">
+Note that the root element has a different background painting area, and thus the '-webkit-background-clip' property has no effect when specified on it. See <a>the backgrounds of special elements</a>.
+</div>
+
+<dl>
+  <dt><dfn value for='-webkit-background-clip'>text</dfn>
+  <dd>Indicates that the background image should clip to the foreground text
+</dl><br>
+
 <div class="example">
 Here's an example showing how to use <code>'-webkit-background-clip': text</code> together with
 <code>-webkit-text-fill-color: transparent</code> to achieve text with a gradient color effect.
@@ -561,11 +573,6 @@ p {
 Browsers that don't support <code>'-webkit-background-clip'</code> or <code>'-webkit-text-fill-color'</code> will use the <code>color</code> declaration as a fallback color.
 </div>
 
-<dl>
-  <dt><dfn value for='-webkit-background-clip'>text</dfn>
-  <dd>Indicates that the background image should clip to the foreground text
-</dl>
-
 <h4 id="the-webkit-text-fill-color">Foreground Color: the <code>
 '-webkit-text-fill-color'</code> property</h4>
 

compatibility.html

@@ -447,7 +447,7 @@ <h4 class="heading settled" data-level="3.4.5" id="the-webkit-background-clip-pr
       <td>none
      <tr>
       <th>Applies to:
-      <td>all elements (Maybe? See <a href="https://github.com/whatwg/compat/issues/39">Issue #39</a>)
+      <td>all elements
      <tr>
       <th>Inherited:
       <td>yes
@@ -465,6 +465,12 @@ <h4 class="heading settled" data-level="3.4.5" id="the-webkit-background-clip-pr
       <td>no
    </table>
    <p>The <code><a class="property" data-link-type="propdesc" href="#propdef--webkit-background-clip">-webkit-background-clip</a></code> property causes the background image to clip to foreground text (including decorations and shadows). The shape of the foreground content (including alpha transparency in the content) is applied as a mask to clip background drawing for the box.</p>
+   <div class="note" role="note"> Note that the root element has a different background painting area, and thus the <a class="property" data-link-type="propdesc" href="#propdef--webkit-background-clip">-webkit-background-clip</a> property has no effect when specified on it. See <a data-link-type="dfn" href="https://drafts.csswg.org/css-backgrounds-3/#special-backgrounds">the backgrounds of special elements</a>. </div>
+   <dl>
+    <dt><dfn class="css" data-dfn-for="-webkit-background-clip" data-dfn-type="value" data-export="" id="valdef--webkit-background-clip-text">text<a class="self-link" href="#valdef--webkit-background-clip-text"></a></dfn> 
+    <dd>Indicates that the background image should clip to the foreground text 
+   </dl>
+   <br> 
    <div class="example" id="example-f30f2a17">
     <a class="self-link" href="#example-f30f2a17"></a> Here’s an example showing how to use <code><a class="property" data-link-type="propdesc" href="#propdef--webkit-background-clip">-webkit-background-clip</a>: text</code> together with <code>-webkit-text-fill-color: transparent</code> to achieve text with a gradient color effect. 
 <pre class="lang-css highlight"><span class="nt">p </span><span class="p">{</span>
@@ -475,10 +481,6 @@ <h4 class="heading settled" data-level="3.4.5" id="the-webkit-background-clip-pr
 <span class="p">}</span></pre>
     <p>Browsers that don’t support <code><a class="property" data-link-type="propdesc" href="#propdef--webkit-background-clip">-webkit-background-clip</a></code> or <code><a class="property" data-link-type="propdesc" href="#propdef--webkit-text-fill-color">-webkit-text-fill-color</a></code> will use the <code>color</code> declaration as a fallback color.</p>
    </div>
-   <dl>
-    <dt><dfn class="css" data-dfn-for="-webkit-background-clip" data-dfn-type="value" data-export="" id="valdef--webkit-background-clip-text">text<a class="self-link" href="#valdef--webkit-background-clip-text"></a></dfn> 
-    <dd>Indicates that the background image should clip to the foreground text 
-   </dl>
    <h4 class="heading settled" data-level="3.4.6" id="the-webkit-text-fill-color"><span class="secno">3.4.6. </span><span class="content">Foreground Color: the <code> <a class="property" data-link-type="propdesc" href="#propdef--webkit-text-fill-color">-webkit-text-fill-color</a></code> property</span><a class="self-link" href="#the-webkit-text-fill-color"></a></h4>
    <table class="def propdef" data-link-for-hint="-webkit-text-fill-color">
     <tbody>
@@ -888,7 +890,7 @@ <h2 class="no-num heading settled" id="property-index"><span class="content">Pro
       <th scope="row"><a class="css" data-link-type="property" href="#propdef--webkit-background-clip">-webkit-background-clip</a>
       <td>text
       <td>none
-      <td>all elements (Maybe? See Issue #39)
+      <td>all elements
       <td>yes
       <td>N/A
       <td>visual