Consolidate test support code.

samples/BUILD.gn

 # Copyright 2014 PDFium 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("../pdfium.gni")
 
 group("samples") {
   deps = [
     ":pdfium_test",
     ":pdfium_diff",
@@ skipping 10 matching lines @@
     defines += [
       "PDF_ENABLE_V8",
     ]
   }
 }
 
 executable("pdfium_test") {
   sources = [
     "image_diff_png.cc",
     "pdfium_test.cc",
+    "../testing/test_support.cpp",
+    "../testing/test_support.h",
   ]
   deps = [
     "//third_party/pdfium",
     # Regardless of whether the library ships against system freetype,
     # always link this binary against the bundled one for consistency
     # of results across platforms.
     "//third_party/pdfium/third_party:fx_freetype",
     ":fx_lpng",
   ]
   if (pdf_enable_v8) {
@@ skipping 42 matching lines @@
     "fx_lpng/src/fx_pngwio.c",
     "fx_lpng/src/fx_pngwrite.c",
     "fx_lpng/src/fx_pngwtran.c",
     "fx_lpng/src/fx_pngwutil.c",
   ]
   include_dirs = [
     "../core/src/fxcodec/fx_zlib/include/",
   ]
   configs += [ ":pdfium_samples_config" ]
 }