Clean up threading model of external extension providers

chrome/app/policy/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 641 matching lines @@
       A blacklist value of * means all extensions are blacklisted and users can only install extensions listed in the whitelist.
 
       By default, all extensions are whitelisted, but if all extensions have been blacklisted by policy, the whitelist can be used to override that policy.''',
           'label': '''Extension IDs to exempt from the blacklist''',
         },
         {
           'name': 'ExtensionInstallForcelist',
           'type': 'list',
           'supported_on': ['chrome.*:9-'],
           'annotations': {
-            'features': {'dynamic_refresh': 0},
+            'features': {'dynamic_refresh': 1},
             'example_value': ['lcncmkcnkcdbbanbjakcencbaoegdjlp;https://clients2.google.com/service/update2/crx'],
           },
           'caption': '''Configure the list of force-installed extensions''',
           'desc': '''Allows you to specify a list of extensions that will be installed silently, without user interaction.
 
       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>). For example: <ph name="EXTENSION_POLICY_EXAMPLE">lcncmkcnkcdbbanbjakcencbaoegdjlp;https://clients2.google.com/service/update2/crx</ph>. For each item, <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> will retrieve the extension specified by the ID from the specified URL and silently install it. The following pages explain how you can host extensions on your own server. About update URLs: <ph name="LINK_TO_EXTENSION_DOC1">http://code.google.com/chrome/extensions/autoupdate.html</ph> , about hosting extensions in general: <ph name="LINK_TO_EXTENSION_DOC2">http://code.google.com/chrome/extensions/hosting.html</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 that are blacklisted in 'ExtensionInstallBlacklist' and not whitelisted, cannot be force-installed by this policy.''',
           'label': '''Extension IDs and update URLs to be silently installed''',
         },
@@ skipping 585 matching lines @@
     {
       'key': '$4',
       'value': 'http://www.chromium.org/developers/how-tos/chrome-frame-getting-started'
     },
     {
       'key': '$5',
       'value': 'http://www.chromium.org/administrators/policy-templates'
     },
   ]
 }