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

chrome/common/extensions/docs/xhr.html

Index: chrome/common/extensions/docs/xhr.html
diff --git a/chrome/common/extensions/docs/xhr.html b/chrome/common/extensions/docs/xhr.html
index b2674f3a45e5e7e8423d4c566433f66d54b2f120..c04f4178b3e98098b75514ab76155b2346ef331f 100644
--- a/chrome/common/extensions/docs/xhr.html
+++ b/chrome/common/extensions/docs/xhr.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>
@@ -501,6 +510,13 @@ prefer HTTPS whenever possible.
                   </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 -->