Negative numbers are not flags.

tools/flags/SkCommandLineFlags.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCommandLineFlags.h"
 #include "SkTDArray.h"
 #include "SkTSort.h"
@@ skipping 264 matching lines @@
                                 i++;
                                 bool value;
                                 if (parse_bool_arg(argv[i], &value)) {
                                     flag->setBool(value);
                                 }
                             }
                             break;
                         case SkFlagInfo::kString_FlagType:
                             flag->resetStrings();
                             // Add all arguments until another flag is reached.
-                            while (i+1 < argc && !SkStrStartsWith(argv[i+1], '-')) {
+                            while (i+1 < argc) {
+                                char* end = NULL;
+                                (void)strtod(argv[i+1], &end); // Negative numbers aren't flags.
+                                if (end == argv[i+1] && SkStrStartsWith(argv[i+1], '-')) {
+                                    break;
+                                }
                                 i++;
                                 flag->append(argv[i]);
                             }
                             break;
                         case SkFlagInfo::kInt_FlagType:
                             i++;
                             flag->setInt(atoi(argv[i]));
                             break;
                         case SkFlagInfo::kDouble_FlagType:
                             i++;
@@ skipping 68 matching lines @@
 }
 
 }  // namespace
 
 bool SkCommandLineFlags::ShouldSkip(const SkTDArray<const char*>& strings, const char* name) {
     return ShouldSkipImpl(strings, name);
 }
 bool SkCommandLineFlags::ShouldSkip(const StringArray& strings, const char* name) {
     return ShouldSkipImpl(strings, name);
 }