Treat bad values passed to --images as a fatal error

bench/nanobench.cpp

Index: bench/nanobench.cpp
diff --git a/bench/nanobench.cpp b/bench/nanobench.cpp
index b461a63ee9757094115c51867c30e54302077826..d66c5ec4373599a31f4b91be9a9f31c048f13425 100644
--- a/bench/nanobench.cpp
+++ b/bench/nanobench.cpp
@@ -605,20 +605,7 @@ public:
         fUseMPDs.push_back() = false;
 
         // Prepare the images for decoding
-        for (int i = 0; i < FLAGS_images.count(); i++) {
-            const char* flag = FLAGS_images[i];
-            if (sk_isdir(flag)) {
-                // If the value passed in is a directory, add all the images
-                SkOSFile::Iter it(flag);
-                SkString file;
-                while (it.next(&file)) {
-                    fImages.push_back() = SkOSPath::Join(flag, file.c_str());
-                }
-            } else if (sk_exists(flag)) {
-                // Also add the value if it is a single image
-                fImages.push_back() = flag;
-            }
-        }
+        SkCommonFlags::collectImages(&fImages);
 
         // Choose the candidate color types for image decoding
         const SkColorType colorTypes[] =