Fix extraction of colour components in CPDF_DIBSource::DownSampleScanline32Bit

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("//testing/test.gni")
 import("pdfium.gni")
 
 config("pdfium_config") {
   cflags = []
   include_dirs = [
@@ skipping 730 matching lines @@
     ":test_support",
   ]
   configs += [ ":pdfium_config" ]
 }
 
 test("pdfium_embeddertests") {
   sources = [
     "core/src/fpdfapi/fpdf_page/fpdf_page_func_embeddertest.cpp",
     "core/src/fpdfapi/fpdf_parser/fpdf_parser_decode_embeddertest.cpp",
     "core/src/fpdfapi/fpdf_parser/fpdf_parser_parser_embeddertest.cpp",
+    "core/src/fpdfapi/fpdf_render/fpdf_render_load_image_embeddertest.cpp",
     "core/src/fpdfapi/fpdf_render/fpdf_render_pattern_embeddertest.cpp",
     "fpdfsdk/src/fpdf_dataavail_embeddertest.cpp",
     "fpdfsdk/src/fpdfdoc_embeddertest.cpp",
     "fpdfsdk/src/fpdfformfill_embeddertest.cpp",
     "fpdfsdk/src/fpdftext_embeddertest.cpp",
     "fpdfsdk/src/fpdfview_c_api_test.c",
     "fpdfsdk/src/fpdfview_c_api_test.h",
     "fpdfsdk/src/fpdfview_embeddertest.cpp",
     "testing/embedder_test.cpp",
     "testing/embedder_test.h",
@@ skipping 13 matching lines @@
       "//v8",
       "//v8:v8_libplatform",
     ]
     include_dirs += [
       "//v8",
       "//v8/include",
     ]
   }
   configs += [ ":pdfium_config" ]
 }