fix misc asserts and checks found by fuzzer

include/effects/SkAlphaThresholdFilter.h

Index: include/effects/SkAlphaThresholdFilter.h
diff --git a/include/effects/SkAlphaThresholdFilter.h b/include/effects/SkAlphaThresholdFilter.h
index 17521b6455d55e59a55884050d70e14b06292c68..033e8d1e54090b63a700d6d5eec936a7799b0590 100644
--- a/include/effects/SkAlphaThresholdFilter.h
+++ b/include/effects/SkAlphaThresholdFilter.h
@@ -20,8 +20,8 @@ public:
      * The 0,0 point of the region corresponds to the upper left corner of the
      * source image.
      */
-    static SkImageFilter* Create(const SkRegion& region, SkScalar innerThreshold,
-                                 SkScalar outerThreshold, SkImageFilter* input = NULL);
+    static SkImageFilter* Create(const SkRegion& region, SkScalar innerMin,
+                                 SkScalar outerMax, SkImageFilter* input = NULL);
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP();
 };