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/rects.cpp b/gm/rects.cpp
index 9600dd5..4b12605 100644
--- a/gm/rects.cpp
+++ b/gm/rects.cpp
@@ -64,7 +64,7 @@
             p.setColor(SK_ColorWHITE);
             p.setAntiAlias(true);
             SkMaskFilter* mf = SkBlurMaskFilter::Create(
-                                   SkBlurMaskFilter::kNormal_BlurStyle,
+                                   kNormal_SkBlurStyle,
                                    SkBlurMask::ConvertRadiusToSigma(SkIntToScalar(5)),
                                    SkBlurMaskFilter::kHighQuality_BlurFlag);
             p.setMaskFilter(mf)->unref();