bind-gen: Implement attribute / operation callback (1 of N)

This patch is exploring how we can implement V8 callback
functions in the new bindings generator.

Attempts to implement the following utilities:
- make_v8_to_blink_value
- bind_blink_api_arguments
- bind_blink_api_call
- bind_return_value
- bind_v8_set_return_value

Bug: 839389
Change-Id: Ie949eca6119806611125fc4e8265601a6888e52b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1880904Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710333}

third_party/blink/renderer/bindings/scripts/bind_gen/code_generation_context.py

@@ -29,6 +29,7 @@ class CodeGenerationContext(object):
         #   attribute name: default value
         cls._context_attrs = {
             # Top-level definition
+            "callback_function": None,
             "callback_interface": None,
             "dictionary": None,
             "interface": None,
@@ -132,6 +133,10 @@ class CodeGenerationContext(object):
         return (self.callback_interface or self.dictionary or self.interface
                 or self.namespace)
 
+    @property
+    def function_like(self):
+        return (self.callback_function or self.constructor or self.operation)
+
     @property
     def is_return_by_argument(self):
         if self.return_type is None:
@@ -164,6 +169,8 @@ class CodeGenerationContext(object):
     def return_type(self):
         if self.attribute_get:
             return self.attribute.idl_type
+        if self.callback_function:
+            return self.callback_function.return_type
         if self.operation:
             return self.operation.return_type
         return None

third_party/blink/renderer/bindings/scripts/web_idl/idl_compiler_test.idl

@@ -12,7 +12,7 @@
 };
 
 namespace TestNamespace {
-  readonly attribute Promise<boolean> attr1;
-  readonly attribute DOMString attr2;
-  void op1();
+  [RaisesException] readonly attribute Promise<boolean> attr1;
+  readonly attribute TestInterfaceConstructor attr2;
+  void op1(long x, boolean y, TestInterfaceConstructor z);
 };