move common blur types into central header

BUG=skia:
R=scroggo@google.com, djsollen@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/253833002

git-svn-id: http://skia.googlecode.com/svn/trunk@14411 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/bleed.cpp b/gm/bleed.cpp
index c343d84..426129b 100644
--- a/gm/bleed.cpp
+++ b/gm/bleed.cpp
@@ -162,7 +162,7 @@
 
         SkPaint paint;
         paint.setFilterLevel(filter);
-        SkMaskFilter* mf = SkBlurMaskFilter::Create(SkBlurMaskFilter::kNormal_BlurStyle,
+        SkMaskFilter* mf = SkBlurMaskFilter::Create(kNormal_SkBlurStyle,
                                          SkBlurMask::ConvertRadiusToSigma(SkIntToScalar(3)));
         paint.setMaskFilter(mf)->unref();