Convert skhello tool to SkFlags API.

tools/skhello.cpp

Index: tools/skhello.cpp
diff --git a/tools/skhello.cpp b/tools/skhello.cpp
index 465806f8faf4cfd13f8688da958091661c844719..8cea1d16403902b0d40925de05e832a7c870589f 100644
--- a/tools/skhello.cpp
+++ b/tools/skhello.cpp
@@ -6,40 +6,28 @@
  */
 
 #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;