Add guard for upcoming SkImage_Lazy change

Change-Id: Ic7acfad8d039172f858ca4b74f8ed3101e719afe
Reviewed-on: https://chromium-review.googlesource.com/1117318Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Brian Osman <brianosman@google.com>
Cr-Commit-Position: refs/heads/master@{#570899}

skia/config/SkUserConfig.h

@@ -193,6 +193,8 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #define SK_SUPPORT_LEGACY_VULKAN_INTERFACE
 #endif
 
+#define SK_SUPPORT_LEGACY_LAZY_IMAGE_DECODE_BEHAVIOR
+
 ///////////////////////// Imported from BUILD.gn and skia_common.gypi
 
 /* In some places Skia can use static initializers for global initialization,