Fix chrome target in Windows GN build.

content/test/BUILD.gn

Index: content/test/BUILD.gn
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index 787c18e6ba9f6a1ee45bf119e286cde81105d508..4cf33a43d374c555975c4f3e05fb4ac86c6111e0 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -56,6 +56,7 @@ static_library("test_support") {
       "//content/browser/speech/proto",
       "//content/public/child:child_sources",
       "//content/gpu",
+      "//content/public/plugin:plugin_sources",
       "//content/public/renderer:renderer_sources",
       "//content/public/utility:utility_sources",
       "//content/shell:pak",
@@ -125,6 +126,7 @@ static_library("test_support") {
 
     if (is_win) {
       deps += [ "//third_party/iaccessible2" ]
+      sources += [ "../app/startup_helper_win.cc" ]
     }
 
     if (!is_android && !is_ios) {