Add warning to policy docs about disabling extensions using devtools.

components/policy/resources/policy_templates.json

 {
 # policy_templates.json - Metafile for policy templates
 #
 # The content of this file is evaluated as a Python expression.
 #
 # This file is used as input to generate the following policy templates:
 # ADM, ADMX+ADML, MCX/plist and html documentation.
 #
 # Policy templates are user interface definitions or documents about the
 # policies that can be used to configure Chrome. Each policy is a name-value
@@ skipping 1822 matching lines @@
           Chrome Web Store.
 
           Each item of the list is a string that contains an extension ID and an update URL delimited by a semicolon (<ph name="SEMICOLON">;</ph>). The extension ID is the 32-letter string found e.g. on <ph name="CHROME_EXTENSIONS_LINK">chrome://extensions</ph> when in developer mode. The update URL should point to an Update Manifest XML document as described at <ph name="LINK_TO_EXTENSION_DOC1">https://developer.chrome.com/extensions/autoupdate</ph>. Note that the update URL set in this policy is only used for the initial installation; subsequent updates of the extension will use the update URL indicated in the extension's manifest.
 
           For each item, <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> will retrieve the extension specified by the extension ID from the update service at the specified update URL and silently install it.
 
           For example, <ph name="EXTENSION_POLICY_EXAMPLE">lcncmkcnkcdbbanbjakcencbaoegdjlp;https://clients2.google.com/service/update2/crx</ph> installs the <ph name="EXTENSION_POLICY_EXAMPLE_EXTENSION_NAME">Google SSL Web Search</ph> extension from the standard Chrome Web Store update URL. For more information about hosting extensions, see: <ph name="LINK_TO_EXTENSION_DOC2">https://developer.chrome.com/extensions/hosting</ph>.
 
           Users will be unable to uninstall extensions that are specified by this policy. If you remove an extension from this list, then it will be automatically uninstalled by <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>. Extensions specified in this list are also automatically whitelisted for installation; the ExtensionsInstallBlacklist does not affect them.
 
-          If this policy is left not set the user can uninstall any extension  in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>.''',
+          Note that the source code of any extension may be altered (potentially
+          rendering the extension dysfunctional) by using Developer Tools. If
+          this is a concern, the DeveloperToolsDisabled policy should be set.
+
+          If this policy is left not set the user can uninstall any extension in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>.''',
           'label': '''Extension IDs and update URLs to be silently installed''',
         },
         {
           'name': 'ExtensionInstallSources',
           'type': 'list',
           'schema': {
             'type': 'array',
             'items': { 'type': 'string' },
             'id': 'ExtensionInstallSources',
           },
@@ skipping 5530 matching lines @@
       'desc': '''Text appended in parentheses next to the policies top-level container to indicate that those policies are of the Recommended level''',
       'text': 'Default Settings (users can override)',
     },
     'doc_complex_policies_on_windows': {
       'desc': '''Text pointing the user to a help article for complex policies on Windows''',
       'text': '''encoded as a JSON string, for details see <ph name="COMPLEX_POLICIES_URL">http://www.chromium.org/administrators/complex-policies-on-windows<ex>http://www.chromium.org/administrators/complex-policies-on-windows</ex></ph>''',
     },
   },
   'placeholders': [],
 }