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

chrome/common/extensions/docs/messaging.html

Index: chrome/common/extensions/docs/messaging.html
diff --git a/chrome/common/extensions/docs/messaging.html b/chrome/common/extensions/docs/messaging.html
index b1a17de00f1224c2f5bf3911af799fc2104c6c47..3cf458c9bbc3edfbe82fbd665ac617e263899269 100644
--- a/chrome/common/extensions/docs/messaging.html
+++ b/chrome/common/extensions/docs/messaging.html
@@ -59,6 +59,15 @@
           <dd>
             Description of this parameter from the json schema.
           </dd>
+          <dd>
+            This parameter was added in version
+            <b><span></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>
@@ -635,6 +644,13 @@ For more examples and for help in viewing the source code, see
                   </div>
                 </div>
 
+                <!-- MIN_VERSION -->
+                <p>
+                  This function was added in version <b><span></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 -->