bind-gen: Initialize cross-component trampolines of IDL interfaces

This patch makes changes only on the new bindings generator,
which is not yet shipped.  No prod change.

Bug: 839389
Change-Id: Iab79e7d82fe064ba30cb540c084577ecca01ceda
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2115136Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752735}

third_party/blink/renderer/bindings/generated_in_modules.gni

@@ -1348,6 +1348,11 @@ if (!is_android) {
   ]
 }
 
+generated_interface_sources_in_modules += [
+  "$root_gen_dir/third_party/blink/renderer/bindings/modules/v8/init_idl_interfaces.cc",
+  "$root_gen_dir/third_party/blink/renderer/bindings/modules/v8/init_idl_interfaces.h",
+]
+
 # Generated sources for testing
 
 generated_interface_sources_for_testing_in_modules = [

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

@@ -3332,6 +3332,85 @@ def generate_interface(interface):
                                 path_manager.gen_path_to(impl_source_path))
 
 
+def generate_init_idl_interfaces(web_idl_database):
+    # Filepaths
+    header_path = PathManager.component_path("modules",
+                                             "init_idl_interfaces.h")
+    source_path = PathManager.component_path("modules",
+                                             "init_idl_interfaces.cc")
+
+    # Root nodes
+    header_node = ListNode(tail="\n")
+    header_node.set_accumulator(CodeGenAccumulator())
+    header_node.set_renderer(MakoRenderer())
+    source_node = ListNode(tail="\n")
+    source_node.set_accumulator(CodeGenAccumulator())
+    source_node.set_renderer(MakoRenderer())
+
+    # Namespaces
+    header_blink_ns = CxxNamespaceNode(name_style.namespace("blink"))
+    source_blink_ns = CxxNamespaceNode(name_style.namespace("blink"))
+    header_bindings_ns = CxxNamespaceNode(name_style.namespace("bindings"))
+    source_bindings_ns = CxxNamespaceNode(name_style.namespace("bindings"))
+    header_blink_ns.body.append(header_bindings_ns)
+    source_blink_ns.body.append(source_bindings_ns)
+
+    # Function nodes
+    func_decl = CxxFuncDeclNode(
+        name="InitIDLInterfaces", arg_decls=[], return_type="void")
+    func_def = CxxFuncDefNode(
+        name="InitIDLInterfaces", arg_decls=[], return_type="void")
+    header_bindings_ns.body.extend([
+        TextNode("""\
+// Initializes cross-component trampolines of IDL interface implementations.\
+"""),
+        func_decl,
+    ])
+    source_bindings_ns.body.append(func_def)
+
+    # Assemble the parts.
+    header_node.extend([
+        make_copyright_header(),
+        EmptyNode(),
+        enclose_with_header_guard(
+            ListNode([
+                make_header_include_directives(header_node.accumulator),
+                EmptyNode(),
+                header_blink_ns,
+            ]), name_style.header_guard(header_path)),
+    ])
+    source_node.extend([
+        make_copyright_header(),
+        EmptyNode(),
+        TextNode("#include \"{}\"".format(header_path)),
+        EmptyNode(),
+        make_header_include_directives(source_node.accumulator),
+        EmptyNode(),
+        source_blink_ns,
+    ])
+
+    init_calls = []
+    for interface in web_idl_database.interfaces:
+        # 'Internals' is the only test-only interface that needs
+        # cross-component trampoline initialization.
+        if interface.identifier == "Internals":
+            continue
+
+        path_manager = PathManager(interface)
+        if path_manager.is_cross_components:
+            source_node.accumulator.add_include_header(
+                path_manager.impl_path(ext="h"))
+
+            class_name = v8_bridge_class_name(interface)
+            init_calls.append(_format("{}::Impl::Init();", class_name))
+    for init_call in sorted(init_calls):
+        func_def.body.append(TextNode(init_call))
+
+    # Write down to the files.
+    write_code_node_to_file(header_node, path_manager.gen_path_to(header_path))
+    write_code_node_to_file(source_node, path_manager.gen_path_to(source_path))
+
+
 def generate_interfaces(web_idl_database):
     # More processes do not mean better performance.  The default size was
     # chosen heuristically.
@@ -3345,3 +3424,5 @@ def generate_interfaces(web_idl_database):
     timeout_in_sec = 3600  # Just enough long time
     pool.map_async(generate_interface,
                    web_idl_database.interfaces).get(timeout_in_sec)
+
+    generate_init_idl_interfaces(web_idl_database)

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

@@ -62,6 +62,14 @@ class PathManager(object):
         }
         cls._is_initialized = True
 
+    @classmethod
+    def component_path(cls, component, filepath):
+        """
+        Returns the relative path to |filepath| in |component|'s directory.
+        """
+        assert cls._is_initialized, cls._REQUIRE_INIT_MESSAGE
+        return posixpath.join(cls._component_reldirs[component], filepath)
+
     @classmethod
     def gen_path_to(cls, path):
         """