Restore SK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS

This disables an "optimization" in Skia that appears to actually cause
a performance regression. After looking, that optimization is probably
unnecessary, and will probably be removed. To facilitate that, this CL
switches it off so we can rebaseline the affected layout tests.

Effectively reverts:
https://chromium-review.googlesource.com/c/chromium/src/+/1334230

Bug: chromium:908566
Change-Id: I634814dabaed09b7f93390f7f4d5fba499317185
Reviewed-on: https://chromium-review.googlesource.com/c/1351761Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612252}

skia/config/SkUserConfig.h

@@ -157,6 +157,10 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #define SK_DISABLE_EXPLICIT_GPU_RESOURCE_ALLOCATION
 #endif
 
+#ifndef SK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS
+#define SK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS
+#endif
+
 // Max. verb count for paths rendered by the edge-AA tessellating path renderer.
 #define GR_AA_TESSELLATOR_MAX_VERB_COUNT 100