Test UKMs in TabActivityWatcher

Adds unit tests that simulate tab activity and test the UKMs logged by
TabMetricsLogger.

Bug: 784639
Change-Id: Id5854b3e2b38b98ecc3d654ac93a24578e26ae3d
Reviewed-on: https://chromium-review.googlesource.com/791868
Commit-Queue: Michael Giuffrida <michaelpg@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520604}

chrome/browser/ui/tabs/tab_activity_watcher.cc

@@ -97,14 +97,6 @@ void TabActivityWatcher::DisableLogTimeoutForTest() {
   per_source_log_timeout_ = base::TimeDelta();
 }
 
-void TabActivityWatcher::SetTabMetricsLoggerForTest(
-    std::unique_ptr<TabMetricsLogger> tab_metrics_logger) {
-  if (tab_metrics_logger)
-    tab_metrics_logger_ = std::move(tab_metrics_logger);
-  else
-    tab_metrics_logger_ = std::make_unique<TabMetricsLoggerImpl>();
-}
-
 void TabActivityWatcher::TabPinnedStateChanged(TabStripModel* tab_strip_model,
                                                content::WebContents* contents,
                                                int index) {

chrome/browser/ui/tabs/tab_activity_watcher.h

@@ -32,9 +32,6 @@ class TabActivityWatcher : public TabStripModelObserver,
   // Forces logging even when a timeout would have prevented it.
   void DisableLogTimeoutForTest();
 
-  void SetTabMetricsLoggerForTest(
-      std::unique_ptr<TabMetricsLogger> tab_metrics_logger);
-
   // Returns the single instance, creating it if necessary.
   static TabActivityWatcher* GetInstance();
 

chrome/browser/ui/tabs/tab_metrics_logger_impl.h

@@ -11,7 +11,6 @@
 // Logs a TabManager.TabMetrics UKM for a tab when requested. Includes
 // information relevant to the tab and its WebContents.
 // Must be used on the UI thread.
-// TODO(michaelpg): Unit test for UKMs.
 class TabMetricsLoggerImpl : public TabMetricsLogger {
  public:
   TabMetricsLoggerImpl();