Bug 1645732 - Add telemetry for Linux window protocol. r=chutten,aosmond

Differential Revision: https://phabricator.services.mozilla.com/D88696

toolkit/components/telemetry/Scalars.yaml

@@ -3621,6 +3621,22 @@ gfx:
     record_in_processes:
       - 'main'
     release_channel_collection: opt-out
+  linux_window_protocol:
+    bug_numbers:
+      - 1645732
+    description: >
+      Windowing protocol on Linux. Can be Wayland, WaylandDRM, XWayland, or X11
+    expires: never
+    kind: string
+    notification_emails:
+      - gfx-telemetry-alerts@mozilla.com
+      - aosmond@mozilla.com
+      - mkaply@mozilla.com
+    products:
+      - 'firefox'
+    record_in_processes:
+      - 'main'
+    release_channel_collection: opt-out
 
 # The following section contains the form autofill related scalars.
 formautofill:

widget/GfxInfoX11.cpp

@@ -17,6 +17,7 @@
 #include "prenv.h"
 #include "nsPrintfCString.h"
 #include "nsWhitespaceTokenizer.h"
+#include "mozilla/Telemetry.h"
 
 #include "GfxInfoX11.h"
 
@@ -706,6 +707,8 @@ GfxInfo::GetWindowProtocol(nsAString& aWindowProtocol) {
   } else {
     aWindowProtocol = GfxDriverInfo::GetWindowProtocol(WindowProtocol::X11);
   }
+  Telemetry::ScalarSet(Telemetry::ScalarID::GFX_LINUX_WINDOW_PROTOCOL,
+                       aWindowProtocol);
   return NS_OK;
 }