Plugin Placeholders: Refactor for platforms that don't support plugins

components/plugins/renderer/BUILD.gn

Index: components/plugins/renderer/BUILD.gn
diff --git a/components/plugins/renderer/BUILD.gn b/components/plugins/renderer/BUILD.gn
index ef7e8f12e10be0827391e41fddd4f2b540ce68e3..446ad999507cc523e0603c866369c0a1e271ce0b 100644
--- a/components/plugins/renderer/BUILD.gn
+++ b/components/plugins/renderer/BUILD.gn
@@ -2,15 +2,21 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/features.gni")
+
 static_library("renderer") {
   sources = [
-    "loadable_plugin_placeholder.cc",
-    "loadable_plugin_placeholder.h",
     "plugin_placeholder.cc",
     "plugin_placeholder.h",
     "webview_plugin.cc",
     "webview_plugin.h",
   ]
+  if (enable_plugins) {
+    sources += [
+      "loadable_plugin_placeholder.cc",
+      "loadable_plugin_placeholder.h",
+    ]
+  }
   if (is_android) {
     sources += [
       "mobile_youtube_plugin.cc",