Add support to previews/ for Server LoFi and LitePages

components/previews/core/previews_black_list.cc

 // 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.
 
 #include "components/previews/core/previews_black_list.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
-#include "base/metrics/histogram_macros.h"
+#include "base/metrics/histogram.h"
 #include "base/optional.h"
 #include "base/time/clock.h"
 #include "components/previews/core/previews_black_list_item.h"
 #include "components/previews/core/previews_experiments.h"
 #include "url/gurl.h"
 
 namespace previews {
 
 namespace {
 
@@ skipping 47 matching lines @@
   }
 }
 
 PreviewsBlackList::~PreviewsBlackList() {}
 
 void PreviewsBlackList::AddPreviewNavigation(const GURL& url,
                                              bool opt_out,
                                              PreviewsType type) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(url.has_host());
-  switch (type) {
-    case PreviewsType::OFFLINE:
-      UMA_HISTOGRAM_BOOLEAN("Previews.OptOut.UserOptedOut.Offline", opt_out);
-      break;
-    default:
-      NOTREACHED();
-  }
+  std::string histogram_name("Previews.OptOut.UserOptedOut.");

[tbansal1, 2017/05/02 21:49:31]

Use StringPiece or   base::StringPrintf to reduce overhead of string
manipulation.

[RyanSturm, 2017/05/02 22:57:18]

Done.

+  histogram_name.append(GetStringNameForType(type));
+
+  base::BooleanHistogram::FactoryGet(
+      histogram_name, base::HistogramBase::kUmaTargetedHistogramFlag)
+      ->Add(opt_out);
   if (opt_out) {
     last_opt_out_time_ = clock_->Now();
   }
   // If the |black_list_item_map_| has been loaded from |opt_out_store_|,
   // synchronous operations will be accurate. Otherwise, queue the task to run
   // asynchronously.
   if (loaded_) {
     AddPreviewNavigationSync(url, opt_out, type);
   } else {
     QueuePendingTask(base::Bind(&PreviewsBlackList::AddPreviewNavigationSync,
@@ skipping 127 matching lines @@
 // static
 std::unique_ptr<PreviewsBlackListItem>
 PreviewsBlackList::CreateHostIndifferentBlackListItem() {
   return base::MakeUnique<PreviewsBlackListItem>(
       params::MaxStoredHistoryLengthForHostIndifferentBlackList(),
       params::HostIndifferentBlackListOptOutThreshold(),
       params::HostIndifferentBlackListPerHostDuration());
 }
 
 }  // namespace previews