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 78a757d7251b25850c11d988425f1852ccb3ed1e..51a84721ad73087ef8432d708973073f2de91a2f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -23537,6 +23537,33 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="GPU.Output.ColorSpace" enum="DXGI_COLOR_SPACE_TYPE">
+  <owner>hubbe@chromium.org</owner>
+  <owner>media-dev@chromium.org</owner>
+  <summary>
+    Records if the output color space of the monitor as reported by DXGI.

[Mark P, 2017/06/26 20:40:11]

"if"
is that typo?  Should it be removed?

[hubbe, 2017/06/26 21:01:21]

Done.

+    Recorded when the gpu process starts.

[Mark P, 2017/06/26 20:40:11]

It looks like this is recorded in a loop, and can be emitted multiple times. 
Yet this description only implies it's emitted once (exactly once).

It's also not emitted if
(FAILED(dxgi_adapter->EnumOutputs(i++, output.GetAddressOf())))

So something in this description needs to be revised.

[hubbe, 2017/06/26 21:01:21]

EnumOutputs really isn't expected to fail.
However, I updated the code and the comment to reflect that these are recorded
for each monitor.

[Mark P, 2017/06/26 21:30:59]

Should you have a CHECK() / LOG(FATAL) in the code then?  Or, if you think it
can fail, at least an UMA_HISTOGRAM to count how often it fails versus succeeds.

[hubbe, 2017/06/26 22:08:58]

If we put in a uma histogram for every windows api that *can* fail but probably
won't we won't have room for any real data. I mean: I can totally do that, but
that's not usually how we write code for windows.

If this fails, it's not a fatal error, we just won't enable HDR output.

[Mark P, 2017/06/26 22:17:48]

The histogram description should be clear then that data can be missing.  E.g.
Excludes monitors on which Windows failed to provide a description of the
monitor.

[hubbe, 2017/06/26 22:24:19]

Seems a little redundant, but ok.

+  </summary>
+</histogram>
+
+<histogram name="GPU.Output.HDR" enum="Boolean">
+  <owner>hubbe@chromium.org</owner>
+  <owner>media-dev@chromium.org</owner>
+  <summary>
+    Records if the output monitor is HDR capable. Recorded when the gpu process
+    starts.
+  </summary>
+</histogram>
+
+<histogram name="GPU.Output.MaxLuminance" units="lumens">
+  <owner>hubbe@chromium.org</owner>
+  <owner>media-dev@chromium.org</owner>
+  <summary>
+    Records if the display maximum lumens as reported by windows.

[Mark P, 2017/06/26 20:40:11]

Uh, the other descriptions don't mention Windows.  And they're emitted in
exactly the same function.  These descriptions should agree.

[hubbe, 2017/06/26 21:01:21]

I updated GPU.Output.ColorSpace
GPU.Output.HDR is generic enough to be used on other platforms, when they add
HDR support...

+    Recorded when the gpu process starts.
+  </summary>
+</histogram>
+
 <histogram name="GPU.ProgramCache.BinaryCacheHitTime" units="microseconds">
   <owner>vmiura@chromium.org</owner>
   <summary>The time to load a gpu program from the program cache.</summary>