PDF: Add UMA to track embedded PDF triggered drive-by downloads.

chrome/common/pdf_uma.h

Index: chrome/common/pdf_uma.h
diff --git a/chrome/common/pdf_uma.h b/chrome/common/pdf_uma.h
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+++ b/chrome/common/pdf_uma.h
@@ -0,0 +1,23 @@
+// Copyright 2016 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.
+
+#ifndef CHROME_COMMON_PDF_UMA_H_
+#define CHROME_COMMON_PDF_UMA_H_
+
+#include "base/macros.h"
+#include "url/gurl.h"

[Ilya Sherman, 2017/05/22 23:00:42]

nit: Where are these used?

[tommycli, 2017/05/23 00:31:59]

Done.

+
+// Must be kept in sync with PDFLoadStatus enum in histograms.xml.
+// This enum should be treated as append-only.
+enum PDFLoadStatus {

[Ilya Sherman, 2017/05/22 23:00:42]

Optional nit: I'd make this an enum class

[tommycli, 2017/05/23 00:31:59]

Done.

+  LOADED_FULL_PAGE_PDF_WITH_PDFIUM = 0,
+  LOADED_EMBEDDED_PDF_WITH_PDFIUM = 1,
+  SHOWED_DISABLED_PLUGIN_PLACEHOLDER_FOR_EMBEDDED_PDF = 2,
+  TRIGGERED_DRIVE_BY_DOWNLOAD = 3,
+  PDF_LOAD_STATUS_COUNT
+};
+
+void ReportPDFLoadStatus(PDFLoadStatus status);

[Ilya Sherman, 2017/05/22 23:00:42]

Hmm, it looks like you're defining a function in the global namespace.  I think
that's discouraged?  I'm not actually 100% sure on what's preferred though -- a
wrapper class, or a wrapper namespace, or neither.

[tommycli, 2017/05/23 00:31:59]

Hey, yeah... I thought the same thing... but I didn't have a strong argument
(other than polluting the global namespace) as to why or what I should wrap this
with... I'll leave this for another reviewer to weigh in.

+
+#endif  // CHROME_COMMON_PDF_UMA_H_