first cut at HQ GPU scaling; refactored existing bicubic scaler

include/core/SkError.h

Index: include/core/SkError.h
diff --git a/include/core/SkError.h b/include/core/SkError.h
index c5af46065f59a7d86d53fde510aa720dcb84a49c..f3f22e9aa05f96780c0c04743e670c4d7e30c8f5 100644
--- a/include/core/SkError.h
+++ b/include/core/SkError.h
@@ -47,7 +47,12 @@ enum SkError {
 
     /** Skia failed while trying to consume some external resource.
      */
-    kParseError_SkError
+    kParseError_SkError,
+    
+    /** Something went wrong internally; could be resource exhaustion but
+      * will often be a bug.
+     */
+    kInternalError_SkError
 };
 
 /** Return the current per-thread error code.  Error codes are "sticky"; they