Create TabManager.TabLifetime UKM.

BUG=776376

Change-Id: I85295f70e14f216c11ecf6c334ee2a39990a9672
Reviewed-on: https://chromium-review.googlesource.com/746532
Commit-Queue: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513310}

chrome/browser/resource_coordinator/tab_manager_web_contents_data.cc

@@ -79,6 +79,7 @@ void TabManager::WebContentsData::DidFinishNavigation(
     return;
   }
 
+  tab_data_.navigation_time = navigation_handle->NavigationStart();
   ukm_source_id_ = ukm::ConvertToSourceId(navigation_handle->GetNavigationId(),
                                           ukm::SourceIdType::NAVIGATION_ID);
 }
@@ -105,6 +106,8 @@ void TabManager::WebContentsData::WebContentsDestroyed() {
                                base::TimeDelta::FromDays(1), 100);
   }
 
+  ReportUKMWhenTabIsClosed();
+
   if (!web_contents()->IsVisible() &&
       tab_data_.last_inactive_time != base::TimeTicks::UnixEpoch()) {
     ReportUKMWhenBackgroundTabIsClosedOrForegrounded(false);
@@ -228,6 +231,15 @@ TimeTicks TabManager::WebContentsData::NowTicks() const {
   return test_tick_clock_->NowTicks();
 }
 
+void TabManager::WebContentsData::ReportUKMWhenTabIsClosed() {
+  if (!ukm_source_id_)
+    return;
+  auto duration = NowTicks() - tab_data_.navigation_time;
+  ukm::builders::TabManager_TabLifetime(ukm_source_id_)
+      .SetTimeSinceNavigation(duration.InMilliseconds())
+      .Record(ukm::UkmRecorder::Get());
+}
+
 void TabManager::WebContentsData::
     ReportUKMWhenBackgroundTabIsClosedOrForegrounded(bool is_foregrounded) {
   if (!ukm_source_id_)
@@ -243,6 +255,7 @@ TabManager::WebContentsData::Data::Data()
     : is_discarded(false),
       discard_count(0),
       is_recently_audible(false),
+      navigation_time(TimeTicks::UnixEpoch()),
       last_audio_change_time(TimeTicks::UnixEpoch()),
       last_discard_time(TimeTicks::UnixEpoch()),
       last_reload_time(TimeTicks::UnixEpoch()),

chrome/browser/resource_coordinator/tab_manager_web_contents_data.h

@@ -169,6 +169,9 @@ class TabManager::WebContentsData
     int discard_count;
     // Is the tab playing audio?
     bool is_recently_audible;
+    // The navigation time associated with this tab. Useful as a reference time
+    // from which to measure UKM event timings.
+    base::TimeTicks navigation_time;
     // Last time the tab started or stopped playing audio (we record the
     // transition time).
     base::TimeTicks last_audio_change_time;
@@ -195,6 +198,7 @@ class TabManager::WebContentsData
   // for more details.
   base::TimeTicks NowTicks() const;
 
+  void ReportUKMWhenTabIsClosed();
   void ReportUKMWhenBackgroundTabIsClosedOrForegrounded(bool is_foregrounded);
 
   // Contains all the needed data for the tab.

tools/metrics/ukm/ukm.xml

@@ -1587,4 +1587,18 @@ be describing additional metrics about the same event.
   </metric>
 </event>
 
+<event name="TabManager.TabLifetime" singular="True">
+  <owner>chrisha@chromium.org</owner>
+  <summary>
+    Collected when a tab is closed, at most once per source.
+  </summary>
+  <metric name="TimeSinceNavigation">
+    <summary>
+      The time when the tab was closed, expressed as the amount of time in MS
+      that has elapsed since the main frame navigation providing the content of
+      the tab.
+    </summary>
+  </metric>
+</event>
+
 </ukm-configuration>