Use new Skia GPU read/write pixel code paths

Change-Id: I8ea66d1b3bb8db174deab690a0cdacc39cf81992
Reviewed-on: https://chromium-review.googlesource.com/973267Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544777}

skia/config/SkUserConfig.h

@@ -208,11 +208,6 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #define SK_SUPPORT_LEGACY_SVG_ARC_TO
 #endif
 
-// Remove after M66 branch to use new read/writePixels implementations
-#ifndef SK_LEGACY_GPU_PIXEL_OPS
-#define SK_LEGACY_GPU_PIXEL_OPS
-#endif
-
 #ifndef SK_SUPPORT_LEGACY_YUV_COLORSPACE
 #define SK_SUPPORT_LEGACY_YUV_COLORSPACE
 #endif