Remove no-op blink-gc-plugin argument.

third_party/WebKit/Source/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("config.gni")
 if (is_clang) {
   import("//build/config/clang/clang.gni")
 }
 
 visibility = [ "//third_party/WebKit/*" ]
@@ skipping 140 matching lines @@
       ]
     }
     if (blink_gc_plugin_option_use_chromium_style_naming) {
       cflags += [
         "-Xclang",
         "-plugin-arg-blink-gc-plugin",
         "-Xclang",
         "use-chromium-style-naming",
       ]
     }
-
-    # TODO(https://crbug.com/689864): remove once the GC plugin has been rolled
-    # with this warning default enabled.
-    cflags += [
-      "-Xclang",
-      "-plugin-arg-blink-gc-plugin",
-      "-Xclang",
-      "warn-stack-allocated-trace-method",
-    ]
   }
 }
 
 # The follow configs apply to all targets except for unit tests, which rely on
 # static initializers.
 config("non_test_config") {
   cflags = []
 
   if (is_clang) {
     cflags += [ "-Wglobal-constructors" ]
   }
 }