Add toString methods to SkImageFilter-derived classes

src/effects/gradients/SkGradientShader.cpp

Index: src/effects/gradients/SkGradientShader.cpp
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 3b73eae6aa46a0b7925e5fbfdd1f8f5f025a67f7..d50afb763838e7e1e819884094ef2233dbaa1d36 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -704,7 +704,7 @@ void SkGradientShaderBase::toString(SkString* str) const {
     str->appendf("%d colors: ", fColorCount);
 
     for (int i = 0; i < fColorCount; ++i) {
-        str->appendHex(fOrigColors[i]);
+        str->appendHex(fOrigColors[i], 8);
         if (i < fColorCount-1) {
             str->append(", ");
         }