Print Preview: Add some debug logging so one can time when print preview operations starts/finishes.

chrome/browser/ui/webui/print_preview_ui.cc

Index: chrome/browser/ui/webui/print_preview_ui.cc
===================================================================
--- chrome/browser/ui/webui/print_preview_ui.cc	(revision 86566)
+++ chrome/browser/ui/webui/print_preview_ui.cc	(working copy)
@@ -38,6 +38,8 @@
 void PrintPreviewUI::OnPreviewDataIsAvailable(int expected_pages_count,
                                               const string16& job_title,
                                               bool modifiable) {
+  VLOG(1) << "Print preview request finished with "
+          << expected_pages_count << " pages";
   FundamentalValue pages_count(expected_pages_count);
   StringValue title(job_title);
   FundamentalValue is_preview_modifiable(modifiable);