Implement Custom Element's class side inheritance

LayoutTests/fast/dom/custom/registration-context-delete-during-register-base-constructor-retrieval-expected.txt

Index: LayoutTests/fast/dom/custom/registration-context-delete-during-register-base-constructor-retrieval-expected.txt
diff --git a/LayoutTests/fast/dom/custom/registration-context-delete-during-register-prototype-retrieval-expected.txt b/LayoutTests/fast/dom/custom/registration-context-delete-during-register-base-constructor-retrieval-expected.txt
similarity index 60%
copy from LayoutTests/fast/dom/custom/registration-context-delete-during-register-prototype-retrieval-expected.txt
copy to LayoutTests/fast/dom/custom/registration-context-delete-during-register-base-constructor-retrieval-expected.txt
index b3fd544cc68db7cc3f8ba820a0a7eae385105783..e0fed56288b6646c199ebdf0e4d56fdba50a99c7 100644
--- a/LayoutTests/fast/dom/custom/registration-context-delete-during-register-prototype-retrieval-expected.txt
+++ b/LayoutTests/fast/dom/custom/registration-context-delete-during-register-base-constructor-retrieval-expected.txt
@@ -1,12 +1,10 @@
-Tests destroying a context during registration at the point when the prototype is retrieved.
+Tests destroying a context during registration at the point when the prototype constructor prototype is retrieved.
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
-PASS destroyed context
-PASS caught expected exception "InvalidStateError: Failed to execute 'registerElement' on 'Document': Registration failed for type 'x-a'. The context is no longer valid."
+PASS caught expected exception "NotSupportedError: Failed to execute 'registerElement' on 'Document': Registration failed for type 'x-a'. Prototype constructor property is not configurable."

[dominicc (has gone to gerrit), 2015/04/09 06:37:57]

It's a concern that "PASS destroyed context" isn't showing up in the test
output, and I'm not sure the error message that is showing up means this test is
running as we want it to. That second error message originates from
prototypeIsValid.

[deepak.s, 2015/04/09 09:50:00]

This is happening because it is failing to configure Prototype constructor
property,
which is valid as per this test also:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

That is why "PASS destroyed context" is not showing up.
Yeah, test is not running as per our expectations.
Either we have to write 'configurable : true' in the constructor property,
we have to test it some other way.

 PASS child done
 PASS successfullyParsed is true
 
 TEST COMPLETE
-