Make the extension API docs point out the minimum version that supports an API call.

chrome/common/extensions/docs/template/api_template.html

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       <!-- SUBTEMPLATES: DO NOT MOVE FROM THIS LOCATION -->
       <!-- In particular, sub-templates that recurse, must be used by allowing
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               </em>
           </dt>
           <dd class="todo" jsdisplay="!$this.description">
             Undocumented.
           </dd>
           <dd jsdisplay="$this.description"
               jsvalues=".innerHTML:$this.description">
             Description of this parameter from the json schema.
           </dd>
+          <dd jsdisplay="$this.min_version">
+            This parameter was added in version
+            <b><span jscontent="$this.min_version"></span></b>.
+            You must omit this parameter in earlier versions,
+            and you may omit it in any version.  If you require this
+            parameter, the manifest key
+            <a href="manifest.html#minimum_chrome_version">minimum_chrome_version</a>
+            can ensure that your extension won't be run in an earlier browser version.
+          </dd>
 
           <!-- OBJECT PROPERTIES -->
           <dd jsdisplay="shouldExpandObject($this)">
             <dl>
               <div jsselect="getPropertyListFromObject($this)">
                 <div transclude="valueTemplate">
                 </div>
               </div>
             </dl>
           </dd>
@@ skipping 279 matching lines @@
                   <pre>function(<span jscontent="getSignatureString(parameters)">Type param1, Type param2</span>) <span class="subdued">{...}</span>);</pre>
                   <dl>
                     <div jsselect="parameters">
                       <div transclude="valueTemplate">
                       </div>
                     </div>
                   </dl>
                   </div>
                 </div>
 
+                <!-- MIN_VERSION -->
+                <p jsdisplay="min_version" >
+                  This function was added in version <b><span jscontent="$this.min_version"></span></b>.
+                  If you require this function, the manifest key
+                  <a href="manifest.html#minimum_chrome_version">minimum_chrome_version</a>
+                  can ensure that your extension won't be run in an earlier browser version.
+                </p>
               </div> <!-- /description -->
 
             </div>  <!-- /apiItem -->
 
           </div>  <!-- /apiGroup -->
 
           <!-- EVENTS -->
           <div jsdisplay="events && events.length > 0" class="apiGroup">
             <a name="events"></a>
             <h3 id="events">Events</h3>
@@ skipping 82 matching lines @@
     _uanchor=1;
     _uff=0;
     urchinTracker();
   }
   catch(e) {/* urchinTracker not available. */}
 </script>
 <!-- end analytics -->
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