Add some metrics for printing with extension

chrome/browser/ui/webui/print_preview/print_preview_handler.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/ui/webui/print_preview/print_preview_handler.h"
 
 #include <ctype.h>
 
 #include <map>
 #include <string>
@@ skipping 89 matching lines @@
   PRINT_TO_PRINTER,
   PRINT_TO_PDF,
   CANCEL,
   FALLBACK_TO_ADVANCED_SETTINGS_DIALOG,
   PREVIEW_FAILED,
   PREVIEW_STARTED,
   INITIATOR_CRASHED,  // UNUSED
   INITIATOR_CLOSED,
   PRINT_WITH_CLOUD_PRINT,
   PRINT_WITH_PRIVET,
+  PRINT_WITH_EXTENSION,
   USERACTION_BUCKET_BOUNDARY
 };
 
 enum PrintSettingsBuckets {
   LANDSCAPE = 0,
   PORTRAIT,
   COLOR,
   BLACK_AND_WHITE,
   COLLATE,
   SIMPLEX,
@@ skipping 757 matching lines @@
       return;
     }
 
     PrintToPrivetPrinter(
         printer_name, print_ticket, capabilities, gfx::Size(width, height));
     return;
   }
 #endif
 
   if (print_with_extension) {
-    // TODO(tbarzic): Record UMA stats.
+    UMA_HISTOGRAM_COUNTS("PrintPreview.PageCount.PrintWithExtension",
+                         page_count);

[Ilya Sherman, 2015/02/21 00:26:39]

I bet that UMA_HISTOGRAM_COUNTS_100 or _10000 would be better for this
histogram, but I understand if you want to keep it inline with the existing
histograms.  (Note that if you want to change the existing histograms to use a
different macro, you should rename those histograms as well, and mark the old
names as <obsolete> in histograms.xml.)

+    ReportUserActionHistogram(PRINT_WITH_EXTENSION);
 
     std::string destination_id;
     std::string print_ticket;
     std::string capabilities;
     int width = 0;
     int height = 0;
     if (!settings->GetString(printing::kSettingDeviceName, &destination_id) ||
         !settings->GetString(printing::kSettingTicket, &print_ticket) ||
         !settings->GetString(printing::kSettingCapabilities, &capabilities) ||
         !settings->GetInteger(printing::kSettingPageWidth, &width) ||
@@ skipping 813 matching lines @@
 
 void PrintPreviewHandler::UnregisterForMergeSession() {
   if (reconcilor_)
     reconcilor_->RemoveMergeSessionObserver(this);
 }
 
 void PrintPreviewHandler::SetPdfSavedClosureForTesting(
     const base::Closure& closure) {
   pdf_file_saved_closure_ = closure;
 }