Add UMA to count the number of Google CAPTCHA pages shown and solved by users.

chrome/browser/page_load_metrics/observers/google_captcha_observer.h

+// Copyright 2015 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_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_GOOGLE_CAPTCHA_OBSERVER_H_
+#define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_GOOGLE_CAPTCHA_OBSERVER_H_
+
+#include "base/macros.h"
+#include "components/page_load_metrics/browser/page_load_metrics_observer.h"
+
+namespace google_captcha_observer {

[Alexei Svitkine (slow), 2015/11/16 16:54:59]

I'll leave it up to owners of this, but I'm not sure it makes sense to have its
own namespace for this class. It's more conventional to use the same namespace
as the overall component. (Unless they owners prefer this style?)

[Matt Welsh, 2015/11/16 18:30:53]

So I'm happy to do whatever makes sense. There is no existing namespace for
other classes in this directory -- from_gws_page_load_metrics_observer.cc uses
the global namespace. Since I'm adding the IsGoogleCaptcha function, I feel that
this should not be global and needs to be nested in some namespace, but I don't
particularly care which -- Charles, do you have a suggestion?

[Charlie Harrison, 2015/11/16 19:12:38]

I'm fine with the google_captcha_observer namespace. I may add another namespace
to all the observers in some later refactor though.

+
+// Returns true if the given URL matches a Google CAPTCHA page.
+bool IsGoogleCaptcha(const GURL& url);
+
+enum GoogleCaptchaEvent {

[Alexei Svitkine (slow), 2015/11/16 16:54:59]

Nit: This can probably live in the .cc if you're not using it elsewhere.

[Matt Welsh, 2015/11/16 18:30:53]

Done.

+  // A Google CAPTCHA page was shown to the user.
+  GOOGLE_CAPTCHA_SHOWN,
+  // A Google CAPTCHA page was solved by the user.
+  GOOGLE_CAPTCHA_SOLVED,
+  // Add new values before this final count.
+  GOOGLE_CAPTCHA_EVENT_BOUNDARY,
+};
+
+class GoogleCaptchaObserver
+    : public page_load_metrics::PageLoadMetricsObserver {
+ public:
+  explicit GoogleCaptchaObserver(
+      page_load_metrics::PageLoadMetricsObservable* metrics);
+
+  // page_load_metrics::PageLoadMetricsObserver implementation:
+  void OnCommit(content::NavigationHandle* navigation_handle) override;
+  void OnRedirect(content::NavigationHandle* navigation_handle) override;
+  void OnPageLoadMetricsGoingAway() override;
+
+ private:
+  page_load_metrics::PageLoadMetricsObservable* const metrics_;
+  DISALLOW_COPY_AND_ASSIGN(GoogleCaptchaObserver);

[Alexei Svitkine (slow), 2015/11/16 16:54:59]

Nit: Add an empty line above this.

[Matt Welsh, 2015/11/16 18:30:53]

Done. Is there a tool to format code according to Chrome style guidelines? (The
google3 C++ formatting seems to be fairly different.)

+};
+
+} // namespace google_captcha_observer
+
+#endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_GOOGLE_CAPTCHA_OBSERVER_H_