Remove SK_SUPPORT_LEGACY_A8_MASKBLITTER and rebaseline

This enables more efficient Skia A8 mask blitters.

Change-Id: Ied97707814e4fd893556b2e77a5426187e6e7b26
Reviewed-on: https://chromium-review.googlesource.com/1019461Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552103}

skia/config/SkUserConfig.h

@@ -199,10 +199,6 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #define SK_DISABLE_RENDER_TARGET_SORTING
 #endif
 
-#ifndef SK_SUPPORT_LEGACY_A8_MASKBLITTER
-#define SK_SUPPORT_LEGACY_A8_MASKBLITTER
-#endif
-
 #ifndef SK_SUPPORT_LEGACY_TILED_BITMAPS
 #define SK_SUPPORT_LEGACY_TILED_BITMAPS
 #endif