Add SkFUZZF to help whitelist imagefilter fuzz failures

src/core/SkFuzzLogging.h

Index: src/core/SkFuzzLogging.h
diff --git a/src/core/SkFuzzLogging.h b/src/core/SkFuzzLogging.h
new file mode 100644
index 0000000000000000000000000000000000000000..8e546e3a06521f3fcc9e51d39641246a95d69eca
--- /dev/null
+++ b/src/core/SkFuzzLogging.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkFuzzLogging_DEFINED
+#define SkFuzzLogging_DEFINED
+
+// Utilities for Skia's fuzzer
+
+// When SK_FUZZ_LOGGING is defined SkDebugfs relevant to image filter fuzzing
+// will be enabled. This allows the filter fuzzing code to white list fuzzer
+// failures based on the output logs.
+// Define this flag in your SkUserConfig.h or in your Make/Build system.
+#ifdef SK_FUZZ_LOGGING
+    #define SkFUZZF(args) SkDebugf("SkFUZZ: "); SkDebugf args
+#else
+    #define SkFUZZF(args)
+#endif
+
+#endif