Fix all relative includes to third_party.

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") {
   testonly = true
   deps = [
     ":pdfium_test",
     ":pdfium_diff",
   ]
 }
 
 config("pdfium_samples_config") {
   defines = [
     "PNG_PREFIX",
     "PNGPREFIX_H",
     "PNG_USE_READ_MACROS",
   ]
+  include_dirs = [ ".." ]
   if (pdf_enable_v8) {
-    defines += [
-      "PDF_ENABLE_V8",
-    ]
+    defines += [ "PDF_ENABLE_V8" ]
   }
 }
 
 executable("pdfium_test") {
   testonly = true
   sources = [
     "image_diff_png.cc",
     "pdfium_test.cc",
   ]
   deps = [
     "//third_party/pdfium:pdfium",
     "//third_party/pdfium:test_support",
+
     # 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) {
-    deps += [
-      "//v8:v8_libplatform",
-    ]
+    deps += [ "//v8:v8_libplatform" ]
     include_dirs = [
       "//v8",
       "//v8/include",
     ]
   }
   configs += [ ":pdfium_samples_config" ]
 }
 
 executable("pdfium_diff") {
   testonly = true
@@ skipping 26 matching lines @@
     "fx_lpng/src/fx_pngrio.c",
     "fx_lpng/src/fx_pngrtran.c",
     "fx_lpng/src/fx_pngrutil.c",
     "fx_lpng/src/fx_pngset.c",
     "fx_lpng/src/fx_pngtrans.c",
     "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/",
-  ]
+  include_dirs = [ "../core/src/fxcodec/fx_zlib/include/" ]
   configs += [ ":pdfium_samples_config" ]
-}
+}