Add some UMA for recent tabs

chrome/browser/android/offline_pages/recent_tab_helper.cc

 // Copyright (c) 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 "chrome/browser/android/offline_pages/recent_tab_helper.h"
 
 #include <queue>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h"
 #include "chrome/browser/android/offline_pages/offline_page_model_factory.h"
 #include "components/offline_pages/offline_page_item.h"
 #include "components/offline_pages/offline_page_model.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/navigation_handle.h"
@@ skipping 60 matching lines @@
 // - compute the set of old 'last_n' pages that have to be purged
 // - delete the pages found in the previous step
 // - snapshot the current web contents
 // Along the chain, the original URL is passed and compared, to detect
 // possible navigation and cancel snapshot in that case.
 void RecentTabHelper::StartSnapshot() {
   if (never_do_snapshots_)
     return;
 
   GURL url = web_contents()->GetLastCommittedURL();
-  if (!page_model_->CanSavePage(url)) {
-    // TODO(dimich): Add UMA. Bug 608112.
+  bool can_save = page_model_->CanSavePage(url);
+  UMA_HISTOGRAM_BOOLEAN("OfflinePages.CanSaveRecentPage", can_save);
+  if (!can_save)
     return;
-  }
 
   snapshot_url_ = url;
 
   // TODO(dimich): Implement automatic cleanup as per design doc, based on
   // storage limits and page age.
   // This algorithm (remove pages before making sure the save was successful)
   // prefers keeping the storage use low and under control by potentially
   // sacrificing the current snapshot.
   page_model_->GetOfflineIdsForClientId(
     client_id(),
@@ skipping 65 matching lines @@
   }
 
   page_model_->SavePage(
       snapshot_url_, client_id(), std::move(archiver),
       base::Bind(&RecentTabHelper::SavePageCallback,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 void RecentTabHelper::SavePageCallback(OfflinePageModel::SavePageResult result,
                                        int64_t offline_id) {
-  // TODO(dimich): add UMA, including result. Bug 608112.
   ReportSnapshotCompleted();
 }
 
 void RecentTabHelper::ReportSnapshotCompleted() {
   snapshot_controller_->PendingSnapshotCompleted();
 }
 
 bool RecentTabHelper::IsSamePage() const {
   return web_contents() &&
          (web_contents()->GetLastCommittedURL() == snapshot_url_);
 }
 
 ClientId RecentTabHelper::client_id() const {
   return ClientId(kClientNamespace, "");
 }
 
 void RecentTabHelper::SetArchiveFactoryForTest(
     std::unique_ptr<TestArchiveFactory> test_archive_factory) {
   test_archive_factory_ = std::move(test_archive_factory);
 }
 
 void RecentTabHelper::SetTaskRunnerForTest(
     const scoped_refptr<base::SingleThreadTaskRunner>& task_runner) {
   snapshot_controller_.reset(new SnapshotController(task_runner, this));
 }
 
 }  // namespace offline_pages