Enable robust decoding of custom wallpaper and allow custom wallpaper on login page

ui/gfx/codec/jpeg_codec.cc

Index: ui/gfx/codec/jpeg_codec.cc
diff --git a/ui/gfx/codec/jpeg_codec.cc b/ui/gfx/codec/jpeg_codec.cc
index 6836143f6eb681c7518d661b941c4328cf2e7fe0..bfa47b97d5537cfff2246b34239fe14054478c62 100644
--- a/ui/gfx/codec/jpeg_codec.cc
+++ b/ui/gfx/codec/jpeg_codec.cc
@@ -42,6 +42,17 @@ void ErrorExit(jpeg_common_struct* cinfo) {
 
 }  // namespace
 
+// This method helps identify at run time which library chromium is using.
+JPEGCodec::LibraryVariant JPEGCodec::JpegLibraryVariant() {
+#if defined(USE_SYSTEM_LIBJPEG)
+  return SYSTEM_LIBJPEG;
+#elif defined(USE_LIBJPEG_TURBO)
+  return LIBJPEG_TURBO;
+#else
+  return IJG_LIBJPEG;
+#endif
+}
+
 // Encoder ---------------------------------------------------------------------
 //
 // This code is based on nsJPEGEncoder from Mozilla.