Add another set of UMA histograms for tab switching on Android.

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 b440c9c353a457e3abe1cf36d8d8bc8e20b7cc55..fe9820a4732969884b6702b0161f7247dcbf086e 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5899,6 +5899,25 @@ other types of suffix sets.
   <summary>Error codes returned by sqlite the web db.</summary>
 </histogram>
 
+<histogram name="Tab.RestoreResult" enum="TabRestoreResult">

[Ilya Sherman, 2013/05/01 01:16:05]

nit: Perhaps re-use the "BooleanSuccess" enum?

[Philippe, 2013/05/02 08:08:47]

Good point.

+  <summary>
+    When the browser restores a tab, whether the load was successful. Loads can
+    fail for instance when there is no connectivity.
+  </summary>
+</histogram>
+
+<histogram name="Tab.RestoreTime" unit="ms">

[Ilya Sherman, 2013/05/01 01:16:05]

This should be "units".  I'm surprised this wasn't caught by the presubmit
check... did you skip that check somehow?

[Philippe, 2013/05/02 08:08:47]

Good catch! The hook was run but the error wasn't propagated  correctly, see the
output:
INFO:root:Loading histograms.xml...
INFO:root:Pretty-printing...
ERROR:root:Unrecognized attribute unit in tag histogram
INFO:root:histograms.xml is correctly pretty-printed.

Presubmit checks took 2.2s to calculate.

Presubmit checks passed.

+  <summary>Load times for successful tab restores.</summary>

[Ilya Sherman, 2013/05/01 01:16:05]

Is this per-tab, or for a whole window, when restoring multiple tabs at once?

[Philippe, 2013/05/02 08:08:47]

I'm using singular now which should be less confusing.

+</histogram>
+
+<histogram name="Tab.RestoreUserPersistence" enum="TabRestoreUserAction">
+  <summary>
+    When the browser restores a tab, whether the user waits for completion of
+    the load or if the user gives up by switching to another tab or leaving
+    Chrome.
+  </summary>
+</histogram>
+
 <histogram name="Tab.SwitchedToForegroundAge" units="ms">
   <summary>Age (in ms) when the tab was switched to foreground.</summary>
 </histogram>
@@ -9454,6 +9473,17 @@ other types of suffix sets.
   </int>
 </enum>
 
+<enum name="TabRestoreResult" type="int">
+  <int value="0" label="Failed"/>
+  <int value="1" label="Succeeded"/>
+</enum>
+
+<enum name="TabRestoreUserAction" type="int">
+  <int value="0" label="WaitForCompletion"/>

[Ilya Sherman, 2013/05/01 01:16:05]

nit: "Wait for completion"

[Philippe, 2013/05/02 08:08:47]

Done.

+  <int value="1" label="SwitchToAnotherTab"/>

[Ilya Sherman, 2013/05/01 01:16:05]

nit: "Switch to another tab"

[Philippe, 2013/05/02 08:08:47]

Done.

+  <int value="2" label="LeaveChrome"/>

[Ilya Sherman, 2013/05/01 01:16:05]

nit: "Leave Chrome"

[Philippe, 2013/05/02 08:08:47]

Done.

+</enum>
+
 <enum name="TabSwitchedToForegroundLaunchedWithURL" type="int">
   <int value="0" label="Launched without an URL"/>
   <int value="1" label="Launched with an URL"/>