Convert some GN test support targets to static libs.

third_party/WebKit/Source/platform/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("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//third_party/WebKit/Source/build/scripts/scripts.gni")
 import("//third_party/WebKit/Source/config.gni")
 import("//third_party/WebKit/Source/platform/platform.gni")
@@ skipping 454 matching lines @@
     include_dirs += [ "//third_party/openmax_dl" ]
     deps += [ "//third_party/openmax_dl/dl" ]
   }
 
   if (remove_webcore_debug_symbols) {
     configs -= [ "//build/config/compiler:default_symbols" ]
     configs += [ "//build/config/compiler:no_symbols" ]
   }
 }
 
-source_set("test_support") {
+static_library("test_support") {
   sources = platform_test_support_files
   visibility += [ "//third_party/WebKit/*" ]
   testonly = true
 
   configs += [
     "//third_party/WebKit/Source:config",
     "//third_party/WebKit/Source:inside_blink",
     "//third_party/WebKit/Source:non_test_config",
   ]
 
@@ skipping 144 matching lines @@
 }
 
 if (current_cpu == "x86" || current_cpu == "x64") {
   source_set("blink_x86_sse") {
     sources = blink_platform_sse_files
     deps = [
       ":blink_common",
     ]
   }
 }