Document the new external extensions path on Mac OS.

chrome/common/extensions/docs/external_extensions.html

Index: chrome/common/extensions/docs/external_extensions.html
diff --git a/chrome/common/extensions/docs/external_extensions.html b/chrome/common/extensions/docs/external_extensions.html
index b26f8e16b02b038e9b19abcfdae53ebae515af51..24346522a75241d285909bbfd59cb4df70445080 100644
--- a/chrome/common/extensions/docs/external_extensions.html
+++ b/chrome/common/extensions/docs/external_extensions.html
@@ -266,8 +266,8 @@
             </li><li>
               <a href="#preferences">Using a preferences file</a>
               <ol>
-                <li style="display: none; ">
-                  <a>h3Name</a>
+                <li>
+                  <a href="#troubleshooting">Troubleshooting Mac OS permissions problems</a>
                 </li>
               </ol>
             </li><li>
@@ -433,8 +433,7 @@ file available to the machine you want to install the extension on.
 <code>\\server\share\extension.crx</code>
 or <code>/home/share/extension.crx</code>.)
 </li>
-<li>Locate the <code>external_extensions.json</code> file
-  under the Google Chrome installation directory.
+<li>Locate the <code>external_extensions.json</code> file.
   If the file doesn't exist, create it.
   The location depends on the operating system.
   <dl>
@@ -444,7 +443,11 @@ or <code>/home/share/extension.crx</code>.)
     Example: <code>c:\Users\Me\AppData\Local\Google\Chrome\Application\6.0.422.0\Extensions\</code>
     </dd>
   <dt> Mac OS X: </dt>
-    <dd> <code>/Applications/Google Chrome.app/Contents/Extensions/</code> </dd>
+    <dd> <code>/Library/Application Support/Google/Chrome/External Extensions/</code> </dd>
+    <p class="note"><b>Note:</b> The external extensions file will only be read if every directory in the path is owned by the user <code>root</code>, the group <code>admin</code>, and is not world readable.  The path must also be free of symbolic links.  These restrictions prevent an unprivileged user from causing extensions to be installed for all users.  See <a href="#troubleshooting">troubleshooting</a> for details.</p>
+    <p class="note">
+    <b>Note:</b> The above path was added in Chrome 16.  Prior versions used a different path, which is now deprecated:
+    <code>/Applications/Google Chrome.app/Contents/Extensions/</code> .</p>
   <dt> Linux: </dt>
     <dd> <code>/opt/google/chrome/extensions/</code> <br>
     <b>Note:</b> Use <code>chmod</code> if necessary
@@ -491,6 +494,18 @@ Example:
 you should see the extension listed. </li>
 </ol>
 
+<h3 id="troubleshooting">Troubleshooting Mac OS permissions problems</h3>
+
+On Mac OS, if you do not see the external extension installed when Chrome is launched, there may be a permissions problem with the external extensions prefs file.  To see if this is the problem, follow these steps:
+
+<ol>
+  <li> Launch the console program, under /Applications/Utilities/Console. </li>
+  <li> Click <code>Console Messages</code> in the left pane. </li>
+  <li> Search for the string <code>Can not read external extensions</code>.  If there is a problem reading the external extensions file, you will find an error message.  Look for another error message directly above it, which should explain the issue.  For example, if you see the following error:
+     <code>Path /Library/Application Support/Google/Chrome is owned by the wrong group.</code>, you need to use <code>chgrp</code> or the Finder's Get Info dialog to make the file owned by the Administrator group.</li>
+  <li> After fixing the issue, relaunch Chrome to try reading the external preferences file again. </li>
+</ol>
+
 <h2 id="registry">Using the Windows registry</h2>
 
 <ol>