[Manifest] Add metrics recording.

content/renderer/manifest/manifest_uma_util.h

+// Copyright 2014 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 CONTENT_RENDERER_MANIFEST_MANIFEST_UMA_UTIL_H_
+#define CONTENT_RENDERER_MANIFEST_MANIFEST_UMA_UTIL_H_
+
+namespace content {
+
+struct Manifest;
+
+class ManifestUmaUtil {
+ public:
+  enum FetchFailureReason {

[Miguel Garcia, 2014/10/02 15:56:42]

can't we forward declare enums now?

[mlamouri (slow - plz ping), 2014/10/02 16:10:55]

Not yet, sadly.

+    FETCH_EMPTY_URL = 0,
+    FETCH_UNSPECIFIED_REASON

[Miguel Garcia, 2014/10/02 15:56:42]

Oh you need all kind of parafernalia for UMA enums :)

See for example
https://cs.corp.google.com/#clankium/src/chrome/browser/content_settings/perm...

Namely, a comment that says to never remove elements and add elements in the
right order

a final FETCH_NUM element.

[mlamouri (slow - plz ping), 2014/10/02 16:10:55]

That's what I do for the internal enum. Not the exposed one.

+  };
+
+  // Record that the Manifest was successfully parsed. If it is an empty
+  // Manifest, it will recorded as so and nothing will happen. Otherwise, the
+  // presence of each properties will be recorded.
+  static void ParseSucceeded(const Manifest& manifest);
+
+  // Record that the Manifest parsing failed.
+  static void ParseFailed();
+
+  // Record that the Manifest fetching succeeded.

[Miguel Garcia, 2014/10/02 15:56:42]

Record whether it succeeded (since you track failures too)

[mlamouri (slow - plz ping), 2014/10/02 16:10:55]

Did not understood.

+  static void FetchSucceeded();
+
+  // Record that the Manifest fetching failed and takes the |reason| why it
+  // failed.
+  static void FetchFailed(FetchFailureReason reason);
+};
+
+} // namespace content
+
+#endif // CONTENT_RENDERER_MANIFEST_MANIFEST_UMA_UTIL_H_