Add histogram WebRTC.UserMediaRequest.Events to allow to track getUserMedia failures and hangs.

content/renderer/media/webrtc_uma_histograms.h

Index: content/renderer/media/webrtc_uma_histograms.h
diff --git a/content/renderer/media/webrtc_uma_histograms.h b/content/renderer/media/webrtc_uma_histograms.h
index 2dfb032db1bf7e875369b2c0886631580034b16b..fa48f7a0dee0d4a9b4efa5cf6155bfa38030bf61 100644
--- a/content/renderer/media/webrtc_uma_histograms.h
+++ b/content/renderer/media/webrtc_uma_histograms.h
@@ -8,9 +8,26 @@
 #include "base/memory/singleton.h"
 #include "base/threading/non_thread_safe.h"
 #include "content/common/content_export.h"
+#include "content/public/common/media_stream_request.h"
 
 namespace content {
 
+// Enum to track UserMediaRequest events. MediaStreamRequestResult events are
+// mapped directly to MediaStreamRequestResult + 10.
+enum UserMediaRequestEvent {
+  USERMEDIAREQUEST_CREATED = 0,

[vrk (LEFT CHROMIUM), 2014/08/04 18:22:17]

I don't think CREATED is a useful histogram value - it will skew the other
percentages, since every CREATED gets counted for every CANCELLED and
NO_RESPONSE value.

I think it'd make more sense to split the values up as follows:
- gUM returned Success
- gUM returned Failure
- gUM cancelled
- gUM called but no response*

*As per other comment, would be better if we could drill down more specifically:
- gUM called, user allowed permission, and no response
- gUM called, user denied permission, and no response
- gUM called, user did not allow/deny permission

[andresp-chromium, 2014/08/04 19:16:23]

This was intended to be an events counter.. in such case it would be acceptable
that events were unrelated and percentage diagrams wouldn't need to make sense
(IMO).

Anyhow when I started following all the code paths with stream generation and so
on it became harder so I am splitting this part into another CL (to prepare
tomorrow) and for now this CL only has stream request result being logged.

On 2014/08/04 18:22:17, Victoria Kirst wrote:

+  USERMEDIAREQUEST_CANCELLED = 1,
+  USERMEDIAREQUEST_NO_RESPONSE = 2,
+  // Unused enum ids so they can be used to track events that don't exist in
+  // MediaStreamRequestResult without destroying existent mappings.
+  USERMEDIAREQUEST_RESULT = 10,

[vrk (LEFT CHROMIUM), 2014/08/04 18:22:17]

ISTM it'd make more sense to have two histograms:

UserMediaRequest.event: histogram of how often gUM returns with success or
failure vs cancel or no response
- UserMediaRequestEvent enum 

UserMediaRequest.result: histogram of results for the gUM calls that do return
either success or failure
- MediaStreamRequestResult enum

So then you wouldn't need to have the USERMEDIAREQUEST_RESULT = 10 stuff.

[andresp-chromium, 2014/08/04 19:16:24]

Totally agree.

On 2014/08/04 18:22:17, Victoria Kirst wrote:

+  NUM_USERMEDIAREQUEST_EVENTS =
+      USERMEDIAREQUEST_RESULT + NUM_MEDIA_REQUEST_RESULTS
+};
+
+void LogUserMediaRequestEvent(UserMediaRequestEvent event);
+void LogUserMediaRequestResult(MediaStreamRequestResult result);
+
 // Helper enum used for histogramming calls to WebRTC APIs from JavaScript.
 enum JavaScriptAPIName {
   WEBKIT_GET_USER_MEDIA,