Log the creation of a dialog boxes using DialogDelegate.

ui/views/window/dialog_delegate.cc

Index: ui/views/window/dialog_delegate.cc
diff --git a/ui/views/window/dialog_delegate.cc b/ui/views/window/dialog_delegate.cc
index fd977cd937c355b53f9d48df75f27412effaa718..6af25ee59accfbcb26ef5379fe67751d4fff6cef 100644
--- a/ui/views/window/dialog_delegate.cc
+++ b/ui/views/window/dialog_delegate.cc
@@ -7,6 +7,7 @@
 #include <utility>
 
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 #include "build/build_config.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/base/l10n/l10n_util.h"
@@ -31,7 +32,9 @@ namespace views {
 ////////////////////////////////////////////////////////////////////////////////
 // DialogDelegate:
 
-DialogDelegate::DialogDelegate() : supports_custom_frame_(true) {}
+DialogDelegate::DialogDelegate() : supports_custom_frame_(true) {
+  UMA_HISTOGRAM_BOOLEAN("Dialog.Delegate.Creation", true);

[msw, 2017/05/01 21:51:30]

Why BOOLEAN? Shouldn't this be UMA_HISTOGRAM_COUNTS_*?

[jwd, 2017/05/03 20:14:40]

No, it's confusing naming. UMA_HISTOGRAM_COUNTS_* is for logging a count of
something, like number of vowels on a page. It would let you answer questions
like "how many pages were seen with >100 vowels" or more abstractly, "how many
times a range of count values were logged". 

BOOLEAN is a special case of an enum histogram. It's for logging an event, like
a vowel was seen. It will just let you answer "how many vowels were seen".

In this case BOOLEAN is the correct histogram.

[msw, 2017/05/03 22:53:22]

Acknowledged.

+}
 
 DialogDelegate::~DialogDelegate() {}