Add toString methods to SkImageFilter-derived classes

tests/PDFPrimitivesTest.cpp

Index: tests/PDFPrimitivesTest.cpp
diff --git a/tests/PDFPrimitivesTest.cpp b/tests/PDFPrimitivesTest.cpp
index ca18b2aebf1775aa71887593aae0f8524bbb0908..3f539e384379e60a60e8f333aa8ee703a8690bc9 100644
--- a/tests/PDFPrimitivesTest.cpp
+++ b/tests/PDFPrimitivesTest.cpp
@@ -443,6 +443,7 @@ public:
         *result = src;
         return true;
     }
+    SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(DummyImageFilter)
     bool visited() const { return fVisited; }
 
@@ -456,6 +457,13 @@ SkFlattenable* DummyImageFilter::CreateProc(SkReadBuffer& buffer) {
     return SkNEW_ARGS(DummyImageFilter, (visited));
 }
 
+#ifndef SK_IGNORE_TO_STRING
+void DummyImageFilter::toString(SkString* str) const {
+    str->appendf("DummyImageFilter: (");
+    str->append(")");
+}
+#endif
+
 };
 
 // Check that PDF rendering of image filters successfully falls back to