Get signals working in the EXTRA_DATA section of MHTML

content/browser/download/mhtml_extra_data_impl.h

+// Copyright (c) 2017 The Chromium Authors. All rights reserved.

[fgorski, 2017/03/28 17:01:12]

nit: drop (c) from the whole patch.

[Pete Williamson, 2017/03/28 18:01:58]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_BROWSER_DOWNLOAD_MHTML_EXTRA_DATA_IMPL_H_
+#define CONTENT_BROWSER_DOWNLOAD_MHTML_EXTRA_DATA_IMPL_H_
+
+#include "content/public/browser/mhtml_extra_data.h"
+
+namespace content {
+
+// Data fields used to build an additional MHTML part in the output file.
+struct MHTMLExtraDataPart {
+  std::string content_type;
+  std::string content_location;
+  std::string body;
+};
+
+// Class used as a data object for WebContents UserData to represent a MHTML
+// part that we plan to write into the output MHTML file.  Each MHTMLExtraPart
+// object in the contained vector lets us hold enough information to generate
+// one MHTML part.  Arbitrary extra MHTML parts to be added into the complete
+// file.  For instance, this might be used for gathering load time signals in
+// debug code for analysis.
+class MHTMLExtraDataImpl : public content::MHTMLExtraData {
+ public:
+  MHTMLExtraDataImpl();
+  ~MHTMLExtraDataImpl() override;
+
+  // Return the vector of parts to be disassembled.
+  std::vector<MHTMLExtraDataPart>& parts() { return parts_; }
+  const std::vector<MHTMLExtraDataPart>& parts() const { return parts_; }
+
+  // Add an extra MHTML part to the data structure stored by the WebContents.
+  // This will take care of generating the boundary line.  This will also set
+  // the content-type and content-location headers to the values provided, and
+  // use the body provided.
+  void StashMHTMLPartForAdditionToPage(const std::string& content_type,

[fgorski, 2017/03/28 17:01:12]

consider renaming to: AddExtraMHTMLPart() here and in the interface.

[Pete Williamson, 2017/03/28 18:01:58]

Done.

+                                       const std::string& content_location,
+                                       const std::string& body) override;
+
+ private:
+  std::vector<MHTMLExtraDataPart> parts_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_DOWNLOAD_MHTML_EXTRA_DATA_IMPL_H_