Merge the latest cpp template from flutter-embedded-linux repo (#131)

Signed-off-by: Hidenori Matsubayashi <[email protected]>

templates/app/runner/command_options.h

@@ -1,4 +1,4 @@
-// Copyright 2021 Sony Corporation. All rights reserved.
+// Copyright 2022 Sony Corporation. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -13,8 +13,6 @@
 #include <unordered_map>
 #include <vector>
 
-// todo: Supports other types besides int, string.
-
 namespace commandline {
 
 namespace {
@@ -56,6 +54,15 @@ class CommandOptions {
                         ReaderInt(), required, true);
   }
 
+  void AddDouble(const std::string& name,
+              const std::string& short_name,
+              const std::string& description,
+              const double& default_value,
+              bool required) {
+    Add<double, ReaderDouble>(name, short_name, description, default_value,
+                        ReaderDouble(), required, true);
+  }
+
   void AddString(const std::string& name,
                  const std::string& short_name,
                  const std::string& description,
@@ -250,6 +257,10 @@ class CommandOptions {
     std::string operator()(const std::string& value) { return value; }
   };
 
+  struct ReaderDouble {
+    double operator()(const std::string& value) { return std::stod(value); }
+  };
+
   class Option {
    public:
     Option(const std::string& name,