Add histogram to track down errors when initializing the audio client.

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 6bf2c915e8f644ad7c823b3aaa1ef5dc45b998a8..f9a80009c3c6f1501d8a45f1cc7436376d59bd97 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -24599,6 +24599,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.Audio.Capture.Win.InitError" units="HRESULT">

[Alexei Svitkine (slow), 2017/02/23 15:29:49]

I think we have an enum for HRESULT. Can you specify it?

[tommi (sloooow) - chröme, 2017/02/23 16:20:56]

It's a 32 bit generic error value. I see we have WinGetLastError, which is a
small subset of HRESULT (via HRESULT_FROM_WIN32).
Is it OK with you if I start adding a definition when we know more about what
errors we will be getting?

+  <owner>tommi@chromium.org</owner>
+  <summary>
+    Error codes from IAudioClient::Initialize() in
+    WASAPIAudioInputStream::InitializeAudioEngine on Windows.
+  </summary>
+</histogram>
+
 <histogram name="Media.Audio.Capture.Win.Open" enum="AudioStreamOpenResult">
   <owner>tommi@chromium.org</owner>
   <summary>