Fix document size not changing when switching between printers.

There was an optimization in preview_generator.js that didn't request a new preview in certain cases.  This CL relaxes the checks so that changing to a new printer always requests a new preview.

In the case where the preview really DOESN'T need to be regenerated an optimization on the C++ side will prevent unneeded regenerations.

BUG=140826


Review URL: https://chromiumcodereview.appspot.com/10826214

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@150699 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/print_preview/preview_generator.js

@@ -258,11 +258,7 @@ cr.define('print_preview', function() {
               !ticketStore.getCustomMargins().equals(
                   ticketStore.getDocumentMargins())) ||
           (this.selectedDestination_ !=
-              this.destinationStore_.selectedDestination &&
-              (this.destinationStore_.selectedDestination.id ==
-                  print_preview.Destination.GooglePromotedId.SAVE_AS_PDF ||
-              this.selectedDestination_.id ==
-                  print_preview.Destination.GooglePromotedId.SAVE_AS_PDF));
+              this.destinationStore_.selectedDestination);
     },
 
     /**