Negative numbers are not flags.

tools/flags/SkCommandLineFlags.cpp

Index: tools/flags/SkCommandLineFlags.cpp
diff --git a/tools/flags/SkCommandLineFlags.cpp b/tools/flags/SkCommandLineFlags.cpp
index 50c193fdf23f309ef92bc081f33676813084d97e..6f1491bf1cb00dcd8bd506c1fec4458dc781860b 100644
--- a/tools/flags/SkCommandLineFlags.cpp
+++ b/tools/flags/SkCommandLineFlags.cpp
@@ -282,7 +282,12 @@ void SkCommandLineFlags::Parse(int argc, char** argv) {
                         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]);
                             }