Histogram the scheme of an origin on the 1st navigation to it.

chrome/browser/profiles/profile_io_data.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/profiles/profile_io_data.h"
 
 #include <stddef.h>
 #include <string>
 #include <utility>
 
@@ skipping 846 matching lines @@
 
 ResourceContext::SaltCallback ProfileIOData::GetMediaDeviceIDSalt() const {
   return base::Bind(&MediaDeviceIDSalt::GetSalt, media_device_id_salt_);
 }
 
 bool ProfileIOData::IsOffTheRecord() const {
   return profile_type() == Profile::INCOGNITO_PROFILE
       || profile_type() == Profile::GUEST_PROFILE;
 }
 
+bool ProfileIOData::HaveAlreadySeenOrigin(const url::Origin& origin) {
+  return origins_seen_.insert(origin).second == false;

[felt, 2016/04/07 02:28:04]

seems unexpected to me (based on method name & description) that this would also
insert the origin in addition to returning true/false

[palmer, 2016/04/07 23:45:43]

What would you rather do?

I want to let the caller not care about the details of keeping track of how we
remember origins we've seen and not seen, and I want to let the caller not have
to adhere to a multi-call protocol such as (hypothetical):

  if (!io_data->HaveAlreadySeen(origin)) {
    // Record UMA...
    io_data->NoteOriginSeen(origin);
  }

[felt, 2016/04/07 23:51:15]

I agree it makes sense to keep it a single method. I was suggesting naming it
something like CalculateRepeatVisit, InsertAndLookupOrigin, or adjusting the
comment to mention it isn't side effect free.

+}
+
 void ProfileIOData::InitializeMetricsEnabledStateOnUIThread() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 #if BUILDFLAG(ANDROID_JAVA_UI)
   // TODO(dwkang): rename or unify the pref for UMA once we have conclusion
   // in crbugs.com/246495.
   // Android has it's own preferences for metrics / crash uploading.
   enable_metrics_.Init(prefs::kCrashReportingEnabled,
                        g_browser_process->local_state());
   enable_metrics_.MoveToThread(
       BrowserThread::GetMessageLoopProxyForThread(BrowserThread::IO));
@@ skipping 441 matching lines @@
       make_scoped_ptr(new DevToolsNetworkTransactionFactory(
           network_controller_handle_.GetController(), shared_session)),
       std::move(backend), true /* set_up_quic_server_info */));
 }
 
 void ProfileIOData::SetCookieSettingsForTesting(
     content_settings::CookieSettings* cookie_settings) {
   DCHECK(!cookie_settings_.get());
   cookie_settings_ = cookie_settings;
 }