Add toString methods to SkImageFilter-derived classes

include/effects/SkDropShadowImageFilter.h

Index: include/effects/SkDropShadowImageFilter.h
diff --git a/include/effects/SkDropShadowImageFilter.h b/include/effects/SkDropShadowImageFilter.h
index a931ad00ffaaf3359b82b0d2a4b05f4a1c89dede..e4c192bc131e7543feb100a653234d3d819a85a0 100644
--- a/include/effects/SkDropShadowImageFilter.h
+++ b/include/effects/SkDropShadowImageFilter.h
@@ -13,9 +13,13 @@ class SK_API SkDropShadowImageFilter : public SkImageFilter {
 public:
     enum ShadowMode {
         kDrawShadowAndForeground_ShadowMode,
-        kDrawShadowOnly_ShadowMode
+        kDrawShadowOnly_ShadowMode,
+
+        kLast_ShadowMode = kDrawShadowOnly_ShadowMode
     };
 
+    static const int kShadowModeCount = kLast_ShadowMode+1;
+
     /** @deprecated use another Create function below instead */
     static SkDropShadowImageFilter* Create(SkScalar dx, SkScalar dy,
                                            SkScalar sigmaX, SkScalar sigmaY, SkColor color,
@@ -45,6 +49,7 @@ public:
     }
 
     virtual void computeFastBounds(const SkRect&, SkRect*) const SK_OVERRIDE;
+    SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkDropShadowImageFilter)
 
 protected: