Do not crash nanobench in debug mode

bench/nanobench.cpp

Index: bench/nanobench.cpp
diff --git a/bench/nanobench.cpp b/bench/nanobench.cpp
index bf99a1eee14db425a5375e07e18ce538ed58314b..0045d53f40ea6ad41b8d8ccf163b3a20492409ea 100644
--- a/bench/nanobench.cpp
+++ b/bench/nanobench.cpp
@@ -639,9 +639,9 @@ public:
             const SkString& path = fImages[fCurrentCodec];
             SkAutoTUnref<SkData> encoded(SkData::NewFromFileName(path.c_str()));
             SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(encoded));
-            SkASSERT(codec);
             if (!codec) {
                 // Nothing to time.
+                SkDebugf("Cannot find codec for %s\n", path.c_str());

[scroggo, 2015/04/24 18:27:24]

I thought you said it printed this without adding this printf? (I've been
running release without your CL and I see a comment like this.) Do we need both?

                 continue;
             }