Initial error handling code

include/core/SkXfermode.h

Index: include/core/SkXfermode.h
diff --git a/include/core/SkXfermode.h b/include/core/SkXfermode.h
index ef00f71b75ecb95bf4a900718efb79356e0a1b35..a5321a5bec4c53ce84793b247ebded31f8fe7a59 100644
--- a/include/core/SkXfermode.h
+++ b/include/core/SkXfermode.h
@@ -79,6 +79,10 @@ public:
      */
     static bool AsCoeff(const SkXfermode*, Coeff* src, Coeff* dst);
 
+    /** Returns true if coeff's value is in the Coeff enum.
+     */
+    static bool IsValidCoeff(Coeff coeff);

[reed1, 2013/09/03 20:25:21]

Move this to some validating helper file?

[sugoi1, 2013/09/04 18:01:10]

Done.

+
     /** List of predefined xfermodes.
         The algebra for the modes uses the following symbols:
         Sa, Sc  - source alpha and color
@@ -160,6 +164,10 @@ public:
      */
     static bool IsMode(const SkXfermode* xfer, Mode mode);
 
+    /** Returns true if mode's value is in the Mode enum.
+     */
+    static bool IsValidMode(Mode mode);
+
     /** Return an SkXfermode object for the specified mode.
      */
     static SkXfermode* Create(Mode mode);