dm: allow multiple --skp flags, allow single files

dm/DM.cpp

 #include "CrashHandler.h"
 #include "DMJsonWriter.h"
 #include "DMSrcSink.h"
 #include "OverwriteLine.h"
 #include "ProcStats.h"
 #include "SkBBHFactory.h"
 #include "SkChecksum.h"
 #include "SkCommonFlags.h"
 #include "SkForceLinking.h"
 #include "SkGraphics.h"
@@ skipping 104 matching lines @@
         Tagged<Src>& s = gSrcs.push_back();
         s.reset(src.detach());
         s.tag = tag;
     }
 }
 
 static void gather_srcs() {
     for (const skiagm::GMRegistry* r = skiagm::GMRegistry::Head(); r; r = r->next()) {
         push_src("gm", new GMSrc(r->factory()));
     }
-    if (!FLAGS_skps.isEmpty()) {
-        SkOSFile::Iter it(FLAGS_skps[0], "skp");
-        for (SkString file; it.next(&file); ) {
-            push_src("skp", new SKPSrc(SkOSPath::Join(FLAGS_skps[0], file.c_str())));
+    for (int i = 0; i < FLAGS_skps.count(); i++) {
+        const char* path = FLAGS_skps[i];
+        if (sk_isdir(path)) {
+            SkOSFile::Iter it(path, "skp");
+            for (SkString file; it.next(&file); ) {
+                push_src("skp", new SKPSrc(SkOSPath::Join(path, file.c_str())));
+            }
+        } else {
+            push_src("skp", new SKPSrc(SkString(path)));
         }
     }
     if (!FLAGS_images.isEmpty()) {
         const char* exts[] = {
             "bmp", "gif", "jpg", "jpeg", "png", "webp", "ktx", "astc", "wbmp", "ico",
             "BMP", "GIF", "JPG", "JPEG", "PNG", "WEBP", "KTX", "ASTC", "WBMP", "ICO",
         };
         for (size_t i = 0; i < SK_ARRAY_COUNT(exts); i++) {
             SkOSFile::Iter it(FLAGS_images[0], exts[i]);
             for (SkString file; it.next(&file); ) {
@@ skipping 391 matching lines @@
     }
     return 0;
 }
 
 #if !defined(SK_BUILD_FOR_IOS) && !defined(SK_BUILD_FOR_NACL)
 int main(int argc, char** argv) {
     SkCommandLineFlags::Parse(argc, argv);
     return dm_main();
 }
 #endif