Differentiate new permissions from old in extension permission update bubble

extensions/common/permissions/permissions_data.h

Index: extensions/common/permissions/permissions_data.h
diff --git a/extensions/common/permissions/permissions_data.h b/extensions/common/permissions/permissions_data.h
index 3b87e79bc393161819710e7d8cca9703cc0857e2..cee22c47f2f2b844bd793a1a87197236cb51cc8e 100644
--- a/extensions/common/permissions/permissions_data.h
+++ b/extensions/common/permissions/permissions_data.h
@@ -140,6 +140,11 @@ class PermissionsData {
   // 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;