[Sync] Initial implementation of foreign sessions suggestions provider.

components/ntp_snippets/content_suggestions_metrics.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/ntp_snippets/content_suggestions_metrics.h"
 
 #include <string>
 
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 25 matching lines @@
     "NewTabPage.ContentSuggestions.MenuOpenedScore";
 const char kHistogramVisitDuration[] =
     "NewTabPage.ContentSuggestions.VisitDuration";
 const char kHistogramMoreButtonShown[] =
     "NewTabPage.ContentSuggestions.MoreButtonShown";
 const char kHistogramMoreButtonClicked[] =
     "NewTabPage.ContentSuggestions.MoreButtonClicked";
 
 const char kPerCategoryHistogramFormat[] = "%s.%s";
 
+// Each suffix here should correspond to an entry under histogram suffix
+// ContentSuggestionCategory in histograms.xml.
 std::string GetCategorySuffix(Category category) {
   // TODO(treib): Find a way to produce a compile error if a known category
   // isn't listed here.
   if (category.IsKnownCategory(KnownCategories::RECENT_TABS))
     return "RecentTabs";
   if (category.IsKnownCategory(KnownCategories::DOWNLOADS))
     return "Downloads";
   if (category.IsKnownCategory(KnownCategories::BOOKMARKS))
     return "Bookmarks";
+  if (category.IsKnownCategory(KnownCategories::FOREIGN_TABS))
+    return "ForeignTabs";
   if (category.IsKnownCategory(KnownCategories::ARTICLES))
     return "Articles";
   // All other categories go into a single "Experimental" bucket.
   return "Experimental";
 }
 
 std::string GetCategoryHistogramName(const char* base_name, Category category) {
   return base::StringPrintf(kPerCategoryHistogramFormat, base_name,
                             GetCategorySuffix(category).c_str());
 }
@@ skipping 154 matching lines @@
 
 void OnMoreButtonClicked(Category category, int position) {
   // The "more" card can appear in addition to the actual suggestions, so add
   // one extra bucket to this histogram.
   LogCategoryHistogramEnumeration(kHistogramMoreButtonClicked, category,
                                   position, kMaxSuggestionsPerCategory + 1);
 }
 
 }  // namespace metrics
 }  // namespace ntp_snippets