remove dead flag SK_LEGACY_PICTURE_SIZE_API

BUG=
TBR=robertphilips

Review URL: https://codereview.chromium.org/787123007

Cr-Commit-Position: refs/heads/master@{#308282}

skia/config/SkUserConfig.h

@@ -265,12 +265,6 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #   define SK_IGNORE_GPU_DITHER
 #endif
 
-#if 0
-#ifndef    SK_LEGACY_PICTURE_SIZE_API
-#   define SK_LEGACY_PICTURE_SIZE_API
-#endif
-#endif
-
 #ifndef    SK_LEGACY_PICTURE_DRAW_API
 #   define SK_LEGACY_PICTURE_DRAW_API
 #endif