Add UMA histograms to track very brief or frequent tabs and JS dialogs.

chrome/browser/ui/tabs/tab_strip_model_stats_recorder.cc

Index: chrome/browser/ui/tabs/tab_strip_model_stats_recorder.cc
diff --git a/chrome/browser/ui/tabs/tab_strip_model_stats_recorder.cc b/chrome/browser/ui/tabs/tab_strip_model_stats_recorder.cc
index e61fc3dd31518c1d04064a864579264b8af04a4f..f09037898bd9041b54d84c70e370054ab8215125 100644
--- a/chrome/browser/ui/tabs/tab_strip_model_stats_recorder.cc
+++ b/chrome/browser/ui/tabs/tab_strip_model_stats_recorder.cc
@@ -10,6 +10,7 @@
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/supports_user_data.h"
+#include "base/time/time.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_iterator.h"
 #include "chrome/browser/ui/browser_list.h"
@@ -42,9 +43,12 @@ class TabStripModelStatsRecorder::TabInfo
     return info;
   }
 
+  base::TimeTicks CreationTime() const { return creation_time_; }

[sky, 2016/01/29 17:25:51]

nit: CreationTime->creation_time

+
  private:
   TabState current_state_ = TabState::INITIAL;
   base::TimeTicks last_state_modified_;
+  base::TimeTicks creation_time_ = base::TimeTicks::Now();
 
   static const char kKey[];
 };
@@ -102,6 +106,12 @@ void TabStripModelStatsRecorder::TabInfo::UpdateState(TabState new_state) {
       NOTREACHED();
       break;
   }
+
+  if (new_state == TabState::CLOSED) {
+    UMA_HISTOGRAM_MEDIUM_TIMES("Tabs.FineTiming.TabLifetime",
+                               now - creation_time_);
+  }
+
   last_state_modified_ = now;
   current_state_ = new_state;
 }
@@ -110,6 +120,7 @@ void TabStripModelStatsRecorder::TabClosingAt(TabStripModel*,
                                               content::WebContents* contents,
                                               int index) {
   TabInfo::Get(contents)->UpdateState(TabState::CLOSED);
+  last_close_time_ = base::TimeTicks::Now();
 
   // Avoid having stale pointer in active_tab_history_
   std::replace(active_tab_history_.begin(), active_tab_history_.end(), contents,
@@ -132,6 +143,23 @@ void TabStripModelStatsRecorder::ActiveTabChanged(
   DCHECK(new_contents);
   TabInfo* tab_info = TabInfo::Get(new_contents);
 
+  if (tab_info->state() == TabState::INITIAL) {
+    // A new tab has been created: log the time since the last one was created.
+    if (!last_creation_time_.is_null()) {
+      UMA_HISTOGRAM_MEDIUM_TIMES("Tabs.FineTiming.TimeSinceLastTabCreated",
+          tab_info->CreationTime() - last_creation_time_);
+    }
+    last_creation_time_ = tab_info->CreationTime();
+
+    // Also log the time since a tab was closed, but only if this is the first
+    // tab that was opened since the closing.
+    if (!last_close_time_.is_null()) {
+      UMA_HISTOGRAM_MEDIUM_TIMES("Tabs.FineTiming.TimeSinceLastTabClosed",
+                                 tab_info->CreationTime() - last_close_time_);
+      last_close_time_ = base::TimeTicks();
+    }
+  }
+
   bool was_inactive = tab_info->state() == TabState::INACTIVE;
   tab_info->UpdateState(TabState::ACTIVE);