Bug 1629357 - Make WebGPU dependent on WebRender feature r=aosmond

WebGPU itself doesn't care about WebRender or even the GPU process.
However, the presentation to canvas as written today only works with WebRender, so
it seems fine to have it as a dependency in general.

An alternative could be to just fail getContext() call if webrender is disabled.

Differential Revision: https://phabricator.services.mozilla.com/D70888

dom/webgpu/mochitest/mochitest.ini

@@ -1,7 +1,8 @@
 [DEFAULT]
 subsuite = webgpu
-prefs = dom.webgpu.enabled=true
-run_if = nightly_build
+run-if = nightly_build && webrender
+prefs =
+	dom.webgpu.enabled=true
 
 [test_enabled.html]
 [test_device_creation.html]

gfx/src/gfxTelemetry.cpp

@@ -26,6 +26,8 @@ const char* FeatureStatusToString(FeatureStatus aStatus) {
       return "unavailable-not-built";
     case FeatureStatus::UnavailableNoAngle:
       return "unavailable-no-angle";
+    case FeatureStatus::UnavailableNoWebRender:
+      return "unavailable-no-webrender";
     case FeatureStatus::CrashedInHandler:
       return "crashed";
     case FeatureStatus::Blocked:

gfx/src/gfxTelemetry.h

@@ -26,6 +26,7 @@ enum class FeatureStatus {
   UnavailableNoHwCompositing,
   UnavailableNotBuilt,
   UnavailableNoAngle,
+  UnavailableNoWebRender,
 
   // This feature crashed immediately when we tried to initialize it, but we
   // were able to recover via SEH (or something similar).

gfx/thebes/gfxPlatform.cpp

@@ -2882,6 +2882,11 @@ void gfxPlatform::InitWebGPUConfig() {
                        "WebGPU can only be enabled in nightly",
                        "WEBGPU_DISABLE_NON_NIGHTLY"_ns);
 #endif
+  if (!UseWebRender()) {
+    feature.ForceDisable(FeatureStatus::UnavailableNoWebRender,
+                         "WebGPU can't present without WebRender",
+                         "FEATURE_FAILURE_WEBGPU_NEED_WEBRENDER"_ns);
+  }
 }
 
 void gfxPlatform::InitOMTPConfig() {

taskcluster/ci/test/mochitest.yml

@@ -555,7 +555,8 @@ mochitest-webgpu:
         by-test-platform:
             .*mingw.*: ["release"]
             .*shippable.*: ["mozilla-central"]
-            default: ["trunk"]
+            (!-shippable).*-qr.*: ["trunk"]
+            default: []
     tier: default
     max-run-time:
         by-test-platform: