Add a histogram to track the type of documents printed (HTML vs PDF)

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

Index: chrome/browser/ui/webui/print_preview/print_preview_handler.cc
diff --git a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
index 7a9693961a36b6508b956476611925a04a84758a..e46c52e7a43b7e6031e5cf32f1c3cff1e9453726 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
+++ b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
@@ -145,6 +145,12 @@ enum PrintSettingsBuckets {
   PRINT_SETTINGS_BUCKET_BOUNDARY
 };
 
+enum PrintDocumentTypeBuckets {

[Ilya Sherman, 2016/12/28 23:25:53]

Please document that this enum is used to back an UMA histogram, and should
therefore be treated as append-only.

[rbpotter, 2016/12/28 23:57:29]

Done. Made similar notes for the two enums above, which also back UMA
histograms.

+  HTML_DOCUMENT = 0,
+  PDF_DOCUMENT,
+  PRINT_DOCUMENT_TYPE_BUCKET_BOUNDARY
+};
+
 void ReportUserActionHistogram(enum UserActionBuckets event) {
   UMA_HISTOGRAM_ENUMERATION("PrintPreview.UserAction", event,
                             USERACTION_BUCKET_BOUNDARY);
@@ -155,6 +161,11 @@ void ReportPrintSettingHistogram(enum PrintSettingsBuckets setting) {
                             PRINT_SETTINGS_BUCKET_BOUNDARY);
 }
 
+void ReportPrintDocumentTypeHistogram(enum PrintDocumentTypeBuckets doctype) {
+  UMA_HISTOGRAM_ENUMERATION("PrintPreview.PrintDocumentType", doctype,
+                            PRINT_DOCUMENT_TYPE_BUCKET_BOUNDARY);
+}
+
 // Name of a dictionary field holding cloud print related data;
 const char kAppState[] = "appState";
 // Name of a dictionary field holding the initiator title.
@@ -804,6 +815,10 @@ void PrintPreviewHandler::HandlePrint(const base::ListValue* args) {
 
   ReportPrintSettingsStats(*settings);
 
+  // Report whether the user printed a PDF or an HTML document.
+  ReportPrintDocumentTypeHistogram(print_preview_ui()->source_is_modifiable() ?
+                                   HTML_DOCUMENT : PDF_DOCUMENT);
+
   // Never try to add headers/footers here. It's already in the generated PDF.
   settings->SetBoolean(printing::kSettingHeaderFooterEnabled, false);