Add toString methods to SkImageFilter-derived classes

src/effects/SkColorFilterImageFilter.cpp

Index: src/effects/SkColorFilterImageFilter.cpp
diff --git a/src/effects/SkColorFilterImageFilter.cpp b/src/effects/SkColorFilterImageFilter.cpp
index 10976d77f0db790c50de8ca3daa0c731ee6e33b6..571d69ce77919d8e0154edf59420ee44e6673a7c 100755
--- a/src/effects/SkColorFilterImageFilter.cpp
+++ b/src/effects/SkColorFilterImageFilter.cpp
@@ -141,3 +141,14 @@ bool SkColorFilterImageFilter::asColorFilter(SkColorFilter** filter) const {
     }
     return false;
 }
+
+#ifndef SK_IGNORE_TO_STRING
+void SkColorFilterImageFilter::toString(SkString* str) const {
+    str->appendf("SkColorFilterImageFilter: (");
+
+    str->appendf("color filter: ");
+    fColorFilter->toString(str);
+
+    str->append(")");
+}
+#endif