bind-gen: Optimize IDL operations that take IDL callback functions

Optimizes the following two parts.
1. Faster conversion to the current execution context.
2. Avoid instantiation of ExceptionState if possible.

Bug: 839389, 1121730
Change-Id: Ia7c03a06def4e1d4a523ec5e699d6b5e7137a35e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391425Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804689}

third_party/blink/renderer/bindings/scripts/bind_gen/blink_v8_bridge.py

@@ -484,7 +484,8 @@ def make_v8_to_blink_value(blink_var_name,
         cg_context and cg_context.operation
         and not (cg_context.is_return_type_promise_type or
                  "RaisesException" in cg_context.operation.extended_attributes)
-        and all(arg.idl_type.type_name == "String"
+        and all((arg.idl_type.type_name == "String" or arg.idl_type.unwrap(
+            typedef=True).is_callback_function)
                 for arg in cg_context.operation.arguments))
     fast_path_cond = None
     fast_path_body_text = None
@@ -496,6 +497,14 @@ def make_v8_to_blink_value(blink_var_name,
         fast_path_cond = "LIKELY({}->IsString())".format(v8_value_expr)
         fast_path_body_text = "{}.Init({}.As<v8::String>());".format(
             blink_var_name, v8_value_expr)
+    elif idl_type.unwrap(typedef=True).is_callback_function:
+        # A key point of this fast path is that it doesn't require an
+        # ExceptionState.
+        fast_path_cond = "LIKELY({}->IsFunction())".format(v8_value_expr)
+        fast_path_body_text = "{} = {}::Create({}.As<v8::Function>());".format(
+            blink_var_name,
+            blink_class_name(idl_type.unwrap().type_definition_object),
+            v8_value_expr)
 
     def create_definition(symbol_node):
         if argument_index is None:

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

@@ -325,7 +325,7 @@ def bind_callback_local_vars(code_node, cg_context):
     local_vars.append(S("execution_context", _format(pattern, _1=_1)))
     node = S("current_execution_context",
              ("ExecutionContext* ${current_execution_context} = "
-              "ExecutionContext::From(${current_script_state});"))
+              "ExecutionContext::From(${current_context});"))
     node.accumulate(
         CodeGenAccumulator.require_include_headers([
             "third_party/blink/renderer/core/execution_context/execution_context.h"
@@ -333,7 +333,7 @@ def bind_callback_local_vars(code_node, cg_context):
     local_vars.append(node)
     node = S("receiver_execution_context",
              ("ExecutionContext* ${receiver_execution_context} = "
-              "ExecutionContext::From(${receiver_script_state});"))
+              "ExecutionContext::From(${receiver_context});"))
     node.accumulate(
         CodeGenAccumulator.require_include_headers([
             "third_party/blink/renderer/core/execution_context/execution_context.h"