Initial error handling code

include/effects/SkFlattenableUtils.h

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkFlattenableUtils_DEFINED
+#define SkFlattenableUtils_DEFINED
+
+#include "SkFlattenable.h"
+
+namespace SkFlattenableUtils {
+
+/** Returns the factory function required to create the given type
+  */
+SkFlattenable::Factory TypeToFactory(SkFlattenable::Type type);

[mtklein, 2013/09/24 22:52:18]

I'm confused why we have both these two functions and the suspiciously similar
static methods on SkFlattenable.

What does this return for kNone?  kSkFlattenable?  Other abstract classes? 
Important to document. I guess, a factory that always returns NULL?

[sugoi1, 2013/09/25 21:15:27]

It's only a question of dependencies. I need to be in "effects" to have access
to all the SkFlattenable derived classes, but SkFlattenable is in "core", so I
wrote the bulk of the functionality in a separate namespace in the effects
library.

+
+/** Checks if typeA is a typeB
+  * For example, if typeA is kSkImageFilter and typeB is kSkFlattenable, this would return true
+  * Inversely, if typeA is kSkFlattenable and typeB is kSkImageFilter, this would return false
+  */
+bool TypeIsA(SkFlattenable::Type typeA, SkFlattenable::Type typeB);
+
+};
+
+#endif