[LoaderTest] Add the gtest pretty printer for ResourceError

third_party/WebKit/Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'ContentDecryptionModuleResult.h',
@@ skipping 1216 matching lines @@
       'image-decoders/ImageDecoderTestHelpers.cpp',
       'image-decoders/bmp/BMPImageDecoderTest.cpp',
       'image-decoders/gif/GIFImageDecoderTest.cpp',
       'image-decoders/jpeg/JPEGImageDecoderTest.cpp',
       'image-decoders/webp/WEBPImageDecoderTest.cpp',
       'threading/BackgroundTaskRunnerTest.cpp',
     ],
     'platform_test_support_files': [
       'graphics/test/FakeGraphicsLayerFactory.cpp',
       'graphics/test/FakeGraphicsLayerFactory.h',
+      'testing/PlatformTestPrinters.cpp',
       'testing/GeometryPrinters.cpp',
       'testing/GeometryPrinters.h',
       'testing/MessageLoopForMojo.h',
       'testing/PaintPrinters.cpp',
       'testing/PaintPrinters.h',
       'testing/PictureMatchers.cpp',
       'testing/PictureMatchers.h',
       'testing/TestingPlatformSupport.cpp',
       'testing/TestingPlatformSupport.h',
       'testing/TestPaintArtifact.cpp',
@@ skipping 30 matching lines @@
       ['OS!="mac"',
         {
           'platform_test_files': [
             'scroll/ScrollAnimatorTest.cpp',
           ],
         }
       ],
     ],
   },
 }