media: Mark EME PersistentUsageRecordSession as stable

This enables EME `persistent-usage-record` session type by default on
all platforms. The actual support of this session type on each platform
depends on the key system and CDM implementations.

See Blink intent-to-ship thread for this feature at
https://groups.google.com/a/chromium.org/g/blink-dev/c/7aTue7FPEuU

Bug: 1081977
Change-Id: I1c05d4b41e15bec3571dfa9c66aa4e269c862004
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2341909Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797292}

chrome/browser/media/encrypted_media_supported_types_browsertest.cc

@@ -204,10 +204,6 @@ class EncryptedMediaSupportedTypesTest : public InProcessBrowserTest {
     test_launcher_utils::RemoveCommandLineSwitch(
         default_command_line, switches::kDisableComponentUpdate, command_line);
 #endif  // BUILDFLAG(ENABLE_LIBRARY_CDMS)
-    command_line->AppendSwitchASCII(
-        switches::kEnableBlinkFeatures,
-        "EncryptedMediaEncryptionSchemeQuery,"
-        "EncryptedMediaPersistentUsageRecordSession");
   }
 
   void SetUpOnMainThread() override {

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -699,7 +699,7 @@
     },
     {
       name: "EncryptedMediaPersistentUsageRecordSession",
-      status: "experimental",
+      status: "stable",
     },
     {
       name: "EnterKeyHintAttribute",