Reland "remove SK_SUPPORT_LEGACY_SVG_ARC_TO"

This reverts commit 46f49dac.

Reason for revert: reverting the original change breaks other bots, such as https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%281%29 an it does not fix the problem on  WebKit Mac 10.13 Retina anyway.

Original change's description:
> Revert "remove SK_SUPPORT_LEGACY_SVG_ARC_TO"
> 
> This reverts commit 05ee0393.
> 
> Reason for revert: Sheriff reverting due to several paint-invalidation failing on the bot WebKit Mac 10.13 Retina.
> See https://crbug.com/891230
> 
> Original change's description:
> > remove SK_SUPPORT_LEGACY_SVG_ARC_TO
> > 
> > Change-Id: I330bdfe4dcbfed55a03385043e703af6fe070ffd
> > Reviewed-on: https://chromium-review.googlesource.com/1254341
> > Commit-Queue: Mike Reed <reed@chromium.org>
> > Reviewed-by: Florin Malita <fmalita@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#595627}
> 
> TBR=fmalita@chromium.org,reed@chromium.org
> 
> Change-Id: Ica1ccdd43953772d40c70d22f3fc399df7dd56b1
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 891230
> Reviewed-on: https://chromium-review.googlesource.com/1256825
> Reviewed-by: Camille Lamy <clamy@chromium.org>
> Commit-Queue: Camille Lamy <clamy@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#595805}

TBR=fmalita@chromium.org,clamy@chromium.org,reed@chromium.org

Change-Id: If0cd979dc3772397f1631d01efc8e08911ecd98c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 891230
Reviewed-on: https://chromium-review.googlesource.com/1256375Reviewed-by: Sorin Jianu <sorin@chromium.org>
Commit-Queue: Sorin Jianu <sorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595834}

skia/config/SkUserConfig.h

@@ -155,11 +155,6 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #define SK_SUPPORT_LEGACY_TILED_BITMAPS
 #endif
 
-// remove after rebaselining svg layout tests
-#ifndef SK_SUPPORT_LEGACY_SVG_ARC_TO
-#define SK_SUPPORT_LEGACY_SVG_ARC_TO
-#endif
-
 // Max. verb count for paths rendered by the edge-AA tessellating path renderer.
 #define GR_AA_TESSELLATOR_MAX_VERB_COUNT 100