Revert "Turn on new image blur for chrome."

This reverts commit 270b4e2b.

Reason for revert: causes msan regression in fuzzer

BUG=789812

TBR=danakj@chromium.org

Original change's description:
> Turn on new image blur for chrome.
>
> BUG=472742
>
> Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel
> Change-Id: Iddaaf37132faf2698c09ae0851c741fb78d97656
> Reviewed-on: https://chromium-review.googlesource.com/791010
> Reviewed-by: danakj <danakj@chromium.org>
> Reviewed-by: Florin Malita <fmalita@chromium.org>
> Commit-Queue: Herb Derby <herb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#519831}

TBR=danakj@chromium.org,fmalita@chromium.org,herb@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 472742
Change-Id: Ia7a31e8ec46679b69e2bad02896921da45dc279a
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel
Reviewed-on: https://chromium-review.googlesource.com/801150
Commit-Queue: Herb Derby <herb@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520628}

skia/config/SkUserConfig.h

@@ -204,6 +204,10 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #define SK_USE_LEGACY_DISTANCE_FIELDS
 #endif
 
+#ifndef SK_SUPPORT_LEGACY_BLUR_IMAGE
+#define SK_SUPPORT_LEGACY_BLUR_IMAGE
+#endif
+
 // Skia is enabling this feature soon. Chrome probably does
 // not want it for M64
 #ifndef SK_DISABLE_EXPLICIT_GPU_RESOURCE_ALLOCATION