Add minimum size for using distance fields.

src/gpu/effects/GrDistanceFieldTextureEffect.cpp

Index: src/gpu/effects/GrDistanceFieldTextureEffect.cpp
diff --git a/src/gpu/effects/GrDistanceFieldTextureEffect.cpp b/src/gpu/effects/GrDistanceFieldTextureEffect.cpp
index fc7fe54501e6bda8b71a649e23f6bcd9f5a3e94d..2309edf064e2143550f4dff25fff65ef078f7085 100755
--- a/src/gpu/effects/GrDistanceFieldTextureEffect.cpp
+++ b/src/gpu/effects/GrDistanceFieldTextureEffect.cpp
@@ -17,7 +17,7 @@
 #include "gl/builders/GrGLProgramBuilder.h"
 
 // Assuming a radius of the diagonal of the fragment, hence a factor of sqrt(2)/2
-#define SK_DistanceFieldAAFactor     "0.7071"
+#define SK_DistanceFieldAAFactor     "0.65"
 
 struct DistanceFieldBatchTracker {
     GrGPInput fInputColorType;