Convert skhello tool to SkFlags API.

tools/skhello.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 "SkCanvas.h"
+#include "SkFlags.h"
 #include "SkGraphics.h"
 #include "SkImageEncoder.h"
 #include "SkString.h"
 
-static void show_help() {
-    SkDebugf("usage: skhello [-o out-dir] [-t 'hello']\n  default output: skhello.png\n");
-}
+DEFINE_string(o, "skhello.png", "The filename to write the image.");
+DEFINE_string(t, "Hello", "The string to write.");
 
 int tool_main(int argc, char** argv);
 int tool_main(int argc, char** argv) {
+    SkFlags::SetUsage("");
+    SkFlags::ParseCommandLine(argc, argv);
+
     SkAutoGraphics ag;
     SkString path("skhello.png");
     SkString text("Hello");
 
-    for (int i = 1; i < argc; i++) {
-        if (!strcmp(argv[i], "--help")) {
-            show_help();
-            return 0;
-        }
-        if (!strcmp(argv[i], "-o")) {
-            if (i == argc-1) {
-                SkDebugf("ERROR: -o needs a following filename\n");
-                return -1;
-            }
-            path.set(argv[i+1]);
-            i += 1; // skip the out dir name
-        } else if (!strcmp(argv[i], "-t")) {
-            if (i == argc-1) {
-                SkDebugf("ERROR: -t needs a following string\n");
-                return -1;
-            }
-            text.set(argv[i+1]);
-            i += 1; // skip the text string
-        }
+    if (!FLAGS_o.isEmpty()) {
+        path.set(FLAGS_o[0]);
+    }
+    if (!FLAGS_t.isEmpty()) {
+        text.set(FLAGS_t[0]);
     }
 
     SkPaint paint;
     paint.setAntiAlias(true);
     paint.setTextSize(SkIntToScalar(30));
     SkScalar width = paint.measureText(text.c_str(), text.size());
     SkScalar spacing = paint.getFontSpacing();
 
     int w = SkScalarRound(width) + 30;
     int h = SkScalarRound(spacing) + 30;
@@ skipping 15 matching lines @@
         SkDebugf("--- failed to write %s\n", path.c_str());
     }
     return !success;
 }
 
 #if !defined SK_BUILD_FOR_IOS
 int main(int argc, char * const argv[]) {
     return tool_main(argc, (char**) argv);
 }
 #endif