expand unitests for color4f

include/core/SkColorFilter.h

Index: include/core/SkColorFilter.h
diff --git a/include/core/SkColorFilter.h b/include/core/SkColorFilter.h
index 211aae696269447ba22a8446e61f9f1baaa97846..aece22e05a594bb5785f07a092529c077465bfe2 100644
--- a/include/core/SkColorFilter.h
+++ b/include/core/SkColorFilter.h
@@ -81,6 +81,10 @@ public:
     */
     virtual uint32_t getFlags() const { return 0; }
 
+    bool supports4f() const {
+        return SkToBool(this->getFlags() & kSupports4f_Flag);
+    }
+
     /**
      *  If this subclass can optimally createa composition with the inner filter, return it as
      *  a new filter (which the caller must unref() when it is done). If no such optimization