Remove the runtime flag for test reports.

These reports are only used for testing, are not web exposed, and the
flag only covers the IDL file anyway, which is unnecessary. This patch
removes that flag.

TBR: japhet@chromium.org
Change-Id: I3a1c63bbbaa2f50cec7c42217a7ce2882ae6f6c2
Reviewed-on: https://chromium-review.googlesource.com/1226077Reviewed-by: Paul Meyer <paulmeyer@chromium.org>
Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Paul Meyer <paulmeyer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592822}

third_party/blink/renderer/core/frame/test_report_body.idl

@@ -5,8 +5,7 @@
 // https://w3c.github.io/reporting/#test-report
 
 [
-    NoInterfaceObject,
-    RuntimeEnabled=TestReporting
+    NoInterfaceObject
 ] interface TestReportBody : ReportBody {
   readonly attribute DOMString message;
 };

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1202,10 +1202,6 @@
       origin_trial_feature_name: "StaleWhileRevalidate",
       status: "experimental",
     },
-    {
-      name: "TestReporting",
-      status: "test",
-    },
     {
       name: "TextUnderlinePositionLeftRight",
       status: "stable",