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 f93cd8c19b27b77f7a7b9088ff47d8f3f0c91eb1..1eaa3c9a18f5eb7554d72871fde071b891ba1250 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5853,6 +5853,24 @@ other types of suffix sets.
   <summary>Error codes returned by sqlite the web db.</summary>
 </histogram>
 
+<histogram name="Tab.RestoreResult" enum="TabRestoreResult">
+  <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">
+  <summary>Load times for successful tab restores.</summary>
+</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 he gives up by switching to another tab or leaving Chrome.

[ppi, 2013/04/30 12:12:27]

supernit: "if they give up"? Does anybody know if we have a policy on
http://en.wikipedia.org/wiki/Singular_they ?

[bulach, 2013/04/30 12:38:11]

how about avoiding the issue altogether and name it something like
RestoreCompletionStatus?

<int value="0" label="RestoredFully"/>
<int value="1" label="SwitchedToAnotherTab"/>
<int value="2" label="SwitchedToAnotherApp"/>

?

[ppi, 2013/04/30 12:42:42]

Please note that strictly speaking "RestoredFully" does not exclude
"SwitchedToAnotherTab". I think I would prefer to keep the first one as
"WaitForCompletion".

Another possible easy fix: s/he/the user/.

On 2013/04/30 12:38:11, bulach wrote:

+  </summary>
+</histogram>
+
 <histogram name="Tab.SwitchedToForegroundAge" units="ms">
   <summary>Age (in ms) when the tab was switched to foreground.</summary>
 </histogram>
@@ -9386,6 +9404,17 @@ 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"/>
+  <int value="1" label="SwitchToAnotherTab"/>
+  <int value="2" label="LeaveChrome"/>
+</enum>
+
 <enum name="TabSwitchedToForegroundLaunchedWithURL" type="int">
   <int value="0" label="Launched without an URL"/>
   <int value="1" label="Launched with an URL"/>