IDL compiler: Stop creating copies of primitive objects.

A lot of copies of 'str' are just waste of memory in the
current design/implementation, so this patch stops creating
copies of primitive objects.

Bug: 839389
Change-Id: I9873986dab0a13340768badfc119100c88eea733
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1774004Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Hitoshi Yoshida <peria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691200}

third_party/blink/renderer/bindings/scripts/web_idl/make_copy.py

@@ -26,12 +26,11 @@ def make_copy(obj, memo=None):
         if copy is not None:
             return copy
 
-    cls = type(obj)
-
     if isinstance(obj, (bool, int, long, float, complex, basestring)):
-        # Subclasses of simple builtin types are expected to have a copy
-        # constructor.
-        return cls.__new__(cls, obj)
+        # Do not create a copy of a primitive (and its subclasses) object.
+        return obj
+
+    cls = type(obj)
 
     if isinstance(obj, (list, tuple, set, frozenset)):
         return cls(map(lambda x: make_copy(x, memo), obj))