CodeGen: Do not use const T* for some user defined types

In concept, we would like constant dictionaries' getters to return
constant references.  However, it can be harmful for developers to
make some sorts of types, e.g. interfaces, constant.

This CL makes it to return a non const reference for those types.


Bug: 839389
Change-Id: I33d4e378e278baf5620c3d8cac39b65a0e590cb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2301712
Commit-Queue: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791744}

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

@@ -372,10 +372,21 @@ def make_dict_member_get(cg_context):
     member = cg_context.dict_member
     blink_member_name = _blink_member_name(member)
     name = blink_member_name.get_api
-    blink_type = blink_type_info(member.idl_type)
+    idl_type = member.idl_type
+    blink_type = blink_type_info(idl_type)
     const_ref_t = blink_type.const_ref_t
     ref_t = blink_type.ref_t
 
+    # Since Blink conventionally prefers non-const references to const
+    # references for the certain types, makes const member's getters return a
+    # non-const reference.  For example, "Node* foo() const;" is preferable to
+    # "const Node* foo() const;".
+    if (idl_type.unwrap().is_interface
+            or idl_type.unwrap().is_callback_interface
+            or idl_type.unwrap().is_callback_function
+            or idl_type.unwrap().is_buffer_source_type):
+        const_ref_t = ref_t
+
     decls = ListNode()
     defs = ListNode()