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

dm/DM.cpp

Index: dm/DM.cpp
diff --git a/dm/DM.cpp b/dm/DM.cpp
index 25a12637887c8ecfc403c93ec1dac66948f321f9..e23e56bb2e8103ccb6ee92facb736c84ca722a39 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -518,29 +518,19 @@ static void gather_srcs() {
             push_src("skp", "", new SKPSrc(path));
         }
     }
-    static const char* const exts[] = {
-        "bmp", "gif", "jpg", "jpeg", "png", "webp", "ktx", "astc", "wbmp", "ico",
-        "BMP", "GIF", "JPG", "JPEG", "PNG", "WEBP", "KTX", "ASTC", "WBMP", "ICO",
-    };
-    for (int i = 0; i < FLAGS_images.count(); i++) {
-        const char* flag = FLAGS_images[i];
-        if (sk_isdir(flag)) {
-            for (size_t j = 0; j < SK_ARRAY_COUNT(exts); j++) {
-                SkOSFile::Iter it(flag, exts[j]);
-                for (SkString file; it.next(&file); ) {
-                    SkString path = SkOSPath::Join(flag, file.c_str());
-                    push_src("image", "decode", new ImageSrc(path)); // Decode entire image
-                    push_codec_srcs(path);
-                    if (brd_supported(exts[j])) {
-                        push_brd_srcs(path);
-                    }
-                }
-            }
-        } else if (sk_exists(flag)) {
-            // assume that FLAGS_images[i] is a valid image if it is a file.
-            push_src("image", "decode", new ImageSrc(flag)); // Decode entire image.
-            push_codec_srcs(flag);
-            push_brd_srcs(flag);
+
+    SkTArray<SkString> images;
+    SkCommonFlags::collectImages(&images);
+    for (auto image : images) {
+        push_src("image", "decode", new ImageSrc(image)); // Decode entire image
+        push_codec_srcs(image);
+        const char* ext = "";
+        int index = image.findLastOf('.');
+        if (index >= 0 && (size_t) ++index < image.size()) {
+            ext = &image.c_str()[index];
+        }
+        if (brd_supported(ext)) {
+            push_brd_srcs(image);
         }
     }
 }