Use updated Skia GPU blur code with various tile mode fixes.

Bug: skia:10818

Change-Id: Iefc3a686b686da4b1287fa97c7684b541b2cfea2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2456291Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Peng Huang <penghuang@chromium.org>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Cr-Commit-Position: refs/heads/master@{#815798}

skia/config/SkUserConfig.h

@@ -212,12 +212,6 @@ SK_API void SkDebugf_FileLine(const char* file,
 #define SK_DISABLE_REDUCE_OPLIST_SPLITTING
 #endif
 
-// Many layout tests and unit tests need to updated/rebased to move to less
-// buggy GPU blur.
-#ifndef SK_USE_LEGACY_GPU_BLUR
-#define SK_USE_LEGACY_GPU_BLUR
-#endif
-
 // Max. verb count for paths rendered by the edge-AA tessellating path renderer.
 #define GR_AA_TESSELLATOR_MAX_VERB_COUNT 100