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

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index b5a898b6df1e8505268736b6a8fad01ac19d7137..bdc35defe0a44bc1f78ebedceab02d012427911c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -17569,6 +17569,30 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="JSDialogs.FineTiming.DialogLifetime" units="ms">
+  <owner>joenotcharles@chromium.org</owner>
+  <summary>
+    Fine-grained (in msec) time between opening a Javascript dialog and closing
+    it, to track very short-lived dialogs.
+  </summary>
+</histogram>
+
+<histogram name="JSDialogs.FineTiming.TimeSinceLastDialogClosed" units="ms">
+  <owner>joenotcharles@chromium.org</owner>
+  <summary>
+    Fine-grained (in msec) time between closing a Javascript dialog and opening
+    another, to track very frequent dialogs.
+  </summary>
+</histogram>
+
+<histogram name="JSDialogs.FineTiming.TimeSinceLastDialogCreated" units="ms">
+  <owner>joenotcharles@chromium.org</owner>
+  <summary>
+    Fine-grained (in msec) time between opening a Javascript dialog and opening
+    another, to track very frequent dialogs.
+  </summary>
+</histogram>
+
 <histogram name="Keyboard.KeystrokeDeltas" units="ms">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
@@ -50693,6 +50717,30 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Tabs.FineTiming.TabLifetime" units="ms">
+  <owner>joenotcharles@chromium.org</owner>
+  <summary>
+    Fine-grained (in msec) time between opening a tab and closing it, to track
+    very short-lived tabs.
+  </summary>
+</histogram>
+
+<histogram name="Tabs.FineTiming.TimeSinceLastTabClosed" units="ms">

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

TimeSinceLastTabClosed is mildly confusing. Time between close and what? Maybe
TimeBetweenTabCloseAndNewTabCreated.

+  <owner>joenotcharles@chromium.org</owner>
+  <summary>
+    Fine-grained (in msec) time between closing a tab and opening another, to
+    track very frequent tabs.
+  </summary>
+</histogram>
+
+<histogram name="Tabs.FineTiming.TimeSinceLastTabCreated" units="ms">
+  <owner>joenotcharles@chromium.org</owner>
+  <summary>
+    Fine-grained (in msec) time between opening a tab and opening another, to
+    track very frequent tabs.
+  </summary>
+</histogram>
+
 <histogram name="Tabs.ForegroundTabAgeAtStartup" units="minutes">
   <owner>lliabraa@chromium.org</owner>
   <summary>