skimage: if --readPath points at an empty dir, create an empty expectations file

tools/skimage_main.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm_expectations.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
@@ skipping 497 matching lines @@
         SkString filename;
         if (iter.next(&filename)) {
             SkString directory(FLAGS_readPath[i]);
             append_path_separator_if_necessary(&directory);
             do {
                 SkString fullname(directory);
                 fullname.append(filename);
                 decodeFileAndWrite(fullname.c_str(), outDirPtr);
             } while (iter.next(&filename));
         } else {
-            decodeFileAndWrite(FLAGS_readPath[i], outDirPtr);
+            // FLAGS_readPath[i] is an empty or nonexistent directory,

[scroggo, 2013/06/19 15:34:09]

I am okay with the spirit of this change, but this else case is supposed to
cover someone calling

skimage --readPath image.png

With this change, that use case is no longer supported.

[epoger, 2013/06/19 15:54:15]

Yup.  It is handy that --readPath can take either folders or files... but it
should probably handle empty directories differently than it does now (it acts
like the folder was a file it couldn't decode).

Anyway, happily, I don't need this change at present... 

+            // so do nothing.
         }
     }
 
     if (!FLAGS_createExpectationsPath.isEmpty()) {
         // Use an empty value for everything besides expectations, since the reader only cares
         // about the expectations.
         Json::Value nullValue;
         Json::Value root = skiagm::CreateJsonTree(gExpectationsToWrite, nullValue, nullValue,
                                                   nullValue, nullValue);
         std::string jsonStdString = root.toStyledString();
@@ skipping 15 matching lines @@
     }
 
     return failed ? -1 : 0;
 }
 
 #if !defined SK_BUILD_FOR_IOS
 int main(int argc, char * const argv[]) {
     return tool_main(argc, (char**) argv);
 }
 #endif