Upstream the iOS web_shell and supporting code

ios/web/shell/web_exe_main.mm

Index: ios/web/shell/web_exe_main.mm
diff --git a/tools/gn/example/hello.cc b/ios/web/shell/web_exe_main.mm
similarity index 50%
copy from tools/gn/example/hello.cc
copy to ios/web/shell/web_exe_main.mm
index c4aa4482949cd0ea980a563e2ea9c5cd2e118365..0e7c58b3a9bfc7454acc4cc0ad985e109d7384d4 100644
--- a/tools/gn/example/hello.cc
+++ b/ios/web/shell/web_exe_main.mm
@@ -2,12 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include <stdio.h>
+#import <UIKit/UIKit.h>
 
-#include "hello_shared.h"
-#include "hello_static.h"
+#import "ios/web/shell/app_delegate.h"
 
 int main(int argc, char* argv[]) {
-  printf("%s, %s\n", GetStaticText(), GetSharedText());
-  return 0;
+  @autoreleasepool {
+    return UIApplicationMain(argc, argv, nil,
+                             NSStringFromClass([AppDelegate class]));
+  }
 }