mac: Add histograms to measure impact of Address Book integration.

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 1f7ad6f405204985db0851d3ca630e044b32d33f..2f58d84a4535723e55f24ffccd3d0dad8057a42b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1809,6 +1809,24 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Autofill.AddressBook.AccessTime" units="ms">
+  <owner>erikchen@chromium.org</owner>
+  <summary>
+    The amount of time spent accessing the OSX Address Book the first time after
+    Chrome was launched. If this time is larger than ~100ms, this it is likely
+    that the user was shown a blocking, modal dialog.
+  </summary>

[Ilya Sherman, 2015/05/14 21:46:28]

Do we really need the raw times, or can we just collapse this to a heuristic
boolean histogram?

[erikchen, 2015/05/15 21:04:50]

Since I haven't seen the raw times, I don't know what heuristic to use yet.
Hence the ~100ms. It might be 5ms it might be 500ms.

+</histogram>
+
+<histogram name="Autofill.AddressBook.ContainedUsefulInformation"
+    enum="Boolean">
+  <owner>erikchen@chromium.org</owner>
+  <summary>
+    After a Chrome is given access to the Mac Address Book, whether any useful
+    information was found.

[Ilya Sherman, 2015/05/14 21:46:28]

I think "useful" is a pretty strong term here.  This histogram is really just
measuring whether the "Me" card had anything in it.  That's a very low bar...

[erikchen, 2015/05/15 21:04:50]

This histogram got replaced by 5 separate histograms.

+  </summary>
+</histogram>
+
 <histogram name="Autofill.AddressBookAvailable" enum="BooleanAvailable">
   <owner>isherman@chromium.org</owner>
   <summary>