Differentiate new permissions from old in extension permission update bubble

extensions/common/permissions/permissions_data.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EXTENSIONS_COMMON_PERMISSIONS_PERMISSIONS_DATA_H_
 #define EXTENSIONS_COMMON_PERMISSIONS_PERMISSIONS_DATA_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 122 matching lines @@
   // there is a content script that matches all hosts, if there is a host
   // permission grants access to all hosts (like <all_urls>) or an api
   // permission that effectively grants access to all hosts (e.g. proxy,
   // network, etc.)
   bool HasEffectiveAccessToAllHosts() const;
 
   // Returns the full list of permission details for messages that should
   // display at install time, in a nested format ready for display.
   PermissionMessages GetPermissionMessages() const;
 
+  // Returns the full list of permission details for messages that should
+  // display at install time, in a nested format ready for display.
+  PermissionMessages GetPermissionMessages(

[Devlin, 2017/04/19 19:18:33]

I wonder if this would be cleaner as GetNewPermissionMessages(const
PermissionSet& granted_permissions), and have this to the diff logic.  That way,
external callers don't have to worry about grabbing the active_permissions from
this class only to pass them right back in.

So the call site would look something like:
PermissionMessages messages =
extension->permissions_data()->GetNewPermissionMessages(*granted_permissions);

WDYT?

[catmullings, 2017/04/20 02:01:59]

Yup, that's sounds good. Will make that change. 

[catmullings, 2017/04/20 02:01:59]

Done.

+      const PermissionSet& permissions) const;
+
   // Returns true if the extension has requested all-hosts permissions (or
   // something close to it), but has had it withheld.
   bool HasWithheldImpliedAllHosts() const;
 
   // Returns true if the |extension| has permission to access and interact with
   // the specified page, in order to do things like inject scripts or modify
   // the content.
   // If this returns false and |error| is non-NULL, |error| will be popualted
   // with the reason the extension cannot access the page.
   bool CanAccessPage(const Extension* extension,
@@ skipping 105 matching lines @@
   mutable TabPermissionsMap tab_specific_permissions_;
 
   mutable std::unique_ptr<base::ThreadChecker> thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(PermissionsData);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_PERMISSIONS_PERMISSIONS_DATA_H_