media: Restrict ProtectedMediaIdentifier permission to secure origins

chrome/browser/media/protected_media_identifier_permission_context.cc

Index: chrome/browser/media/protected_media_identifier_permission_context.cc
diff --git a/chrome/browser/media/protected_media_identifier_permission_context.cc b/chrome/browser/media/protected_media_identifier_permission_context.cc
index 50c2dc51ec53a1f4269eff81c038c44fc6eb40bc..3ef58c85b500a619821eab9d88b2a9166e588769 100644
--- a/chrome/browser/media/protected_media_identifier_permission_context.cc
+++ b/chrome/browser/media/protected_media_identifier_permission_context.cc
@@ -145,9 +145,12 @@ void ProtectedMediaIdentifierPermissionContext::UpdateTabContext(
   }
 }
 
-bool
-ProtectedMediaIdentifierPermissionContext::IsRestrictedToSecureOrigins() const {
-  return false;
+bool ProtectedMediaIdentifierPermissionContext::IsRestrictedToSecureOrigins()
+    const {
+  // EME is not supported on insecure origins, see https://goo.gl/Ks5zf7
+  // Note that origins whitelisted by --unsafely-treat-insecure-origin-as-secure
+  // flag will be treated as "secure" so they will not be affected.
+  return true;
 }
 
 // TODO(xhwang): We should consolidate the "protected content" related pref