When SkFlags encounters an invalid flag, quit.

tools/SkFlags.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 "SkFlags.h"
 
 SkFlagInfo* SkFlags::gHead;
@@ skipping 139 matching lines @@
                             flag->setDouble(atof(argv[i]));
                             break;
                         default:
                             SkASSERT(!"Invalid flag type");
                     }
                     break;
                 }
                 flag = flag->next();
             }
             if (!flagMatched) {
-                SkDebugf("skipping unknown flag %s\n", argv[i]);
+                SkDebugf("Got unknown flag \"%s\". Exiting.\n", argv[i]);
+                exit(-1);
             }
         }
     }
     // Since all of the flags have been set, release the memory used by each
     // flag. FLAGS_x can still be used after this.
     SkFlagInfo* flag = gHead;
     gHead = NULL;
     while (flag != NULL) {
         SkFlagInfo* next = flag->next();
         SkDELETE(flag);
         flag = next;
     }
     if (helpPrinted) {
         exit(0);
     }
 }