v8binding: Supports InvokeAndReportException for type Function.

Web IDL type Function (= any (any...)) is a sort of "arbitrary
function", and used very widely in the web standards.  Its
return value is often discarded, as if its return type is void.

So, this patch supports InvokeAndReportException for type
Function.

Bug: 871208
Change-Id: Icbe56560585c402271363e7c8294d3b0c96b1562
Reviewed-on: https://chromium-review.googlesource.com/1173931
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582843}

third_party/blink/renderer/bindings/templates/callback_function.cpp.tmpl

@@ -146,12 +146,12 @@ v8::Maybe<{{return_cpp_type}}> {{cpp_class}}::Invoke({{argument_declarations | j
   {% endif %}
 }
 
-{% if idl_type == 'void' %}
+{% if idl_type == 'void' or callback_function_name == 'Function' %}
 void {{cpp_class}}::InvokeAndReportException({{argument_declarations | join(', ')}}) {
   v8::TryCatch try_catch(GetIsolate());
   try_catch.SetVerbose(true);
 
-  v8::Maybe<void> maybe_result =
+  v8::Maybe<{{return_cpp_type}}> maybe_result =
       Invoke({{
                  (['callback_this_value'] +
                   (arguments|map(attribute='name')|list)
@@ -171,7 +171,7 @@ v8::Maybe<{{return_cpp_type}}> V8PersistentCallbackFunction<{{cpp_class}}>::Invo
       }});
 }
 
-{% if idl_type == 'void' %}
+{% if idl_type == 'void' or callback_function_name == 'Function' %}
 void V8PersistentCallbackFunction<{{cpp_class}}>::InvokeAndReportException({{argument_declarations | join(', ')}}) {
   Proxy()->InvokeAndReportException(
       {{

third_party/blink/renderer/bindings/templates/callback_function.h.tmpl

@@ -30,7 +30,9 @@ class {{exported}}{{cpp_class}} final : public CallbackFunctionBase {
   // https://heycam.github.io/webidl/#es-invoking-callback-functions
   v8::Maybe<{{return_cpp_type}}> Invoke({{argument_declarations | join(', ')}}) WARN_UNUSED_RESULT;
 
-{% if idl_type == 'void' %}
+{# Type Function is often used as a sort of wild cards, and its return value is
+   often discarded. So, this provides some convenience. #}
+{% if idl_type == 'void' or callback_function_name == 'Function' %}
   // Performs "invoke", and then reports an exception, if any, to the global
   // error handler such as DevTools' console.
   void InvokeAndReportException({{argument_declarations | join(', ')}});
@@ -52,7 +54,7 @@ class V8PersistentCallbackFunction<{{cpp_class}}> final : public V8PersistentCal
   V8CallbackFunction* ToNonV8Persistent() { return Proxy(); }
 
   v8::Maybe<{{return_cpp_type}}> Invoke({{argument_declarations | join(', ')}}) WARN_UNUSED_RESULT;
-{% if idl_type == 'void' %}
+{% if idl_type == 'void' or callback_function_name == 'Function' %}
   {{exported}}void InvokeAndReportException({{argument_declarations | join(', ')}});
 {% endif %}