Add toString methods to SkImageFilter-derived classes

src/effects/SkMergeImageFilter.cpp

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkMergeImageFilter.h"
 #include "SkCanvas.h"
 #include "SkDevice.h"
@@ skipping 122 matching lines @@
     return Create(common.inputs(), count, NULL, &common.cropRect(), common.uniqueID());
 }
 
 void SkMergeImageFilter::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writeBool(fModes != NULL);
     if (fModes) {
         buffer.writeByteArray(fModes, countInputs() * sizeof(fModes[0]));
     }
 }
+
+#ifndef SK_IGNORE_TO_STRING
+void SkMergeImageFilter::toString(SkString* str) const {
+    str->appendf("SkMergeImageFilter: (");
+    
+    for (int i = 0; i < this->countInputs(); ++i) {
+        SkImageFilter* filter = this->getInput(i);
+        str->appendf("%d: (", i);
+        filter->toString(str);
+        str->appendf(")");
+    }
+
+    str->append(")");
+}
+#endif