Make mojom-generated C++ string constants really constant.

mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 {%- if variant -%}
 {%-   set variant_path = "%s-%s"|format(module.path, variant) -%}
 {%- else -%}
 {%-   set variant_path = module.path -%}
 {%- endif -%}
 
@@ skipping 17 matching lines @@
 {%-   for namespace in namespaces_as_array|reverse %}
 }  // namespace {{namespace}}
 {%-   endfor %}
 {%- endmacro %}
 
 #ifndef {{header_guard}}
 #define {{header_guard}}
 
 #include <stdint.h>
 
+#include <limits>
 #include <type_traits>
 #include <utility>
 
 #include "base/callback.h"
 #include "base/optional.h"
 #include "mojo/public/cpp/bindings/associated_interface_ptr.h"
 #include "mojo/public/cpp/bindings/associated_interface_ptr_info.h"
 #include "mojo/public/cpp/bindings/associated_interface_request.h"
 #include "mojo/public/cpp/bindings/interface_ptr.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
@@ skipping 41 matching lines @@
 
 {#--- Enums #}
 {%- if variant %}
 {%-   for enum in enums %}
 using {{enum.name}} = {{enum.name}};  // Alias for definition in the parent namespace.
 {%-   endfor %}
 {%- endif %}
 
 {#--- Constants #}
 {%- for constant in module.constants %}
-{#-   To be consistent with constants defined inside interfaces, only make
-      integral types compile-time constants. #}
-{%-   if constant.kind|is_integral_kind %}
-const {{constant.kind|cpp_pod_type}} {{constant.name}} = {{constant|constant_value}};
-{%-   else %}
-extern const {{constant.kind|cpp_pod_type}} {{constant.name}};
-{%-   endif %}
+{{constant|format_constant_declaration}};
 {%- endfor %}
 
 {#--- Interface Forward Declarations -#}
 {%  for interface in interfaces %}
 class {{interface.name}};
 using {{interface.name}}Ptr = mojo::InterfacePtr<{{interface.name}}>;
 using {{interface.name}}PtrInfo = mojo::InterfacePtrInfo<{{interface.name}}>;
 using ThreadSafe{{interface.name}}Ptr =
     mojo::ThreadSafeInterfacePtr<{{interface.name}}>;
 using {{interface.name}}Request = mojo::InterfaceRequest<{{interface.name}}>;
@@ skipping 105 matching lines @@
 {#--- Union Serialization Helpers -#}
 {%  if unions %}
 {%-   for union in unions %}
 {%      include "union_traits_declaration.tmpl" %}
 {%-   endfor %}
 {%- endif %}
 
 }  // namespace mojo
 
 #endif  // {{header_guard}}