Log the creation of dialog boxes using DialogDelegateView and BubbleDialogDelegateView.

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 8b5dd5c804e344df612a0a8530a124c680d98038..06c4021a6140aa23b607c9284f994d9f182d9af1 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -11853,6 +11853,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Dialog.Create" enum="BooleanCreated">
+  <owner>pdyson@chromium.org</owner>
+  <summary>Counts the number times dialog boxes are created.</summary>

[msw, 2017/05/11 00:54:39]

I think we need to get more specific here... you have two or three fairly
closely related metrics and it's not clear to casual observers how they are
related (overlap, comparison, etc.) For example, BubbleDialogDelegateView is-a
DialogDelegateView, and DialogDelegateView is-a DialogDelegate, so you'll record
all three creat[e|ion] metrics for one BubbleDialogDelegateView instantiation,
and you'll record both DialogDelegateView and DialogDelegate for one non-bubble
DialogDelegateView instantiation, right? This seems broken.

[pdyson, 2017/05/11 05:54:01]

I've added to the comments here and below to make this clearer. We have found a
very large gap between the number of dialogs that we are counting specifically
in Dialog.Creation and the overall number in Dialog.Delegate.Creation. So we
will start counting the classes in between to see where the discrepancy might
lie. There is also another cl coming where we count many more specific child
classes. This current cl will allow us to see where the gaps are more precisely.

+</histogram>
+
 <histogram name="Dialog.Creation" enum="DialogName">
   <owner>pdyson@chromium.org</owner>
   <summary>
@@ -85202,6 +85207,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <affected-histogram name="DesktopIOSPromotion.VariationSigninReason"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="DialogTypes" separator="." ordering="prefix">
+  <suffix name="DelegateView"
+      label="Counts dialog boxes created using DialogDelegateView."/>
+  <suffix name="BubbleDialogDelegateView"
+      label="Counts dialog boxes created using BubbleDialogDelegateView."/>
+  <affected-histogram name="Dialog.Create"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="DiskUsagePerUserCount" separator=".">
   <suffix name="1User" label="Only 1 user exists on device."/>
   <suffix name="2Users" label="2 users exist on device."/>