Create --disable-extensions-except switch

chrome/browser/extensions/extension_service.h

Index: chrome/browser/extensions/extension_service.h
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index 556cc4f388d1cf775eb14147623418b4c4d5afd5..aed1cb19083eaf649110025134002b941eef53c7 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -456,6 +456,15 @@ class ExtensionService
     external_updates_finished_callback_ = callback;
   }
 
+  void AddExtensionToWhitelist(const std::string& extensionId) {

[Devlin, 2016/07/27 17:00:59]

"Whitelist" here is still pretty vague.  But this might be moot with other
comments.

[catmullings, 2016/08/04 22:59:30]

Done.

+    enabled_extensions_whitelist_.insert(extensionId);
+  }
+
+  bool IsExtensionWhitelisted(const std::string& extensionId) {
+    return enabled_extensions_whitelist_.find(extensionId) !=
+           enabled_extensions_whitelist_.end();
+  }
+
  private:
   // Reloads the specified extension, sending the onLaunched() event to it if it
   // currently has any window showing. |be_noisy| determines whether noisy
@@ -616,6 +625,10 @@ class ExtensionService
   // These extensions should appear in registry_.
   extensions::ExtensionSet greylist_;
 
+  // Set of whitelisted enabled extensions loaded from the
+  // --disable-extensions-except command line flag.
+  std::set<std::string> enabled_extensions_whitelist_;
+
   // The list of extension installs delayed for various reasons.  The reason
   // for delayed install is stored in ExtensionPrefs. These are not part of
   // ExtensionRegistry because they are not yet installed.