Make gm use SkFlags.

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 20 matching lines @@
     bool helpPrinted = false;
     // Loop over argv, starting with 1, since the first is just the name of the program.
     for (int i = 1; i < argc; i++) {
         if (0 == strcmp("-h", argv[i]) || 0 == strcmp("--h", argv[i])
                 || 0 == strcmp("-help", argv[i]) || 0 == strcmp("--help", argv[i])) {
             // Print help message.
             SkDebugf("%s\n%s\n", argv[0], gUsage.c_str());
             SkDebugf("Flags:\n");
             SkFlagInfo* flag = SkFlags::gHead;
             while (flag != NULL) {
-                SkDebugf("\t--%s:\ttype: %s\tdefault: %s\n", flag->name().c_str(),
-                          flag->typeAsString().c_str(), flag->defaultValue().c_str());
+                SkDebugf("\t--%s:\ttype: %s", flag->name().c_str(),
+                          flag->typeAsString().c_str());
+                if (flag->defaultValue().size() > 0) {
+                    SkDebugf("\tdefault: %s", flag->defaultValue().c_str());
+                }
+                SkDebugf("\n");
                 const SkString& help = flag->help();
                 size_t length = help.size();
                 const char* currLine = help.c_str();
                 const char* stop = currLine + length;
                 while (currLine < stop) {
                     if (strlen(currLine) < LINE_LENGTH) {
                         // Only one line length's worth of text left.
                         SkDebugf("\t\t%s\n", currLine);
                         break;
                     }
@@ skipping 72 matching lines @@
     gHead = NULL;
     while (flag != NULL) {
         SkFlagInfo* next = flag->next();
         SkDELETE(flag);
         flag = next;
     }
     if (helpPrinted) {
         exit(0);
     }
 }