Fix //content/test:test_support under component builds.

content/ppapi_plugin/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.
 
-source_set("ppapi_plugin") {
+group("ppapi_plugin") {
+  visibility = [ "//content/*" ]
+
+  if (is_component_build) {
+    public_deps = [
+      "//content",
+    ]
+  } else {
+    public_deps = [
+      ":ppapi_plugin_sources",
+    ]
+  }
+}
+
+source_set("ppapi_plugin_sources") {
   visibility = [ "//content/*" ]
 
   sources = [
     "broker_process_dispatcher.cc",
     "broker_process_dispatcher.h",
     "plugin_process_dispatcher.cc",
     "plugin_process_dispatcher.h",
     "ppapi_blink_platform_impl.cc",
     "ppapi_blink_platform_impl.h",
     "ppapi_broker_main.cc",
@@ skipping 12 matching lines @@
     "//ppapi/proxy:ipc",
     "//skia",
     "//third_party/icu",
     "//third_party/WebKit/public:blink",
     "//third_party/mojo/src/mojo/public/interfaces/application",
     "//ui/base",
     "//ui/gfx",
     "//ui/gfx/geometry",
   ]
 }