bgsound must use the HTMLUnknownElement interface

As specified here:
https://html.spec.whatwg.org/#bgsound

This causes one less fail on:
http://w3c-test.org/html/semantics/interfaces.html

Review URL: https://codereview.chromium.org/728763006

git-svn-id: svn://svn.chromium.org/blink/trunk@186905 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/fast/dom/wrapper-classes-expected.txt

@@ -213,6 +213,10 @@ PASS tagClassString('bdo') is "HTMLElement"
 FAIL tagPrototypeClassString('bdo') should be HTMLElementPrototype. Was Object.
 PASS tagConstructorClassString('bdo') is "Function"
 PASS tagConstructorName('bdo') is "HTMLElement"
+PASS tagClassString('bgsound') is "HTMLUnknownElement"
+FAIL tagPrototypeClassString('bgsound') should be HTMLUnknownElementPrototype. Was Object.
+PASS tagConstructorClassString('bgsound') is "Function"
+PASS tagConstructorName('bgsound') is "HTMLUnknownElement"
 PASS tagClassString('big') is "HTMLElement"
 FAIL tagPrototypeClassString('big') should be HTMLElementPrototype. Was Object.
 PASS tagConstructorClassString('big') is "Function"

third_party/WebKit/LayoutTests/fast/dom/wrapper-classes.html

@@ -157,6 +157,7 @@
     testTag("base", "HTMLBaseElement");
     testTag("basefont", "HTMLElement");
     testTag("bdo", "HTMLElement");
+    testTag("bgsound", "HTMLUnknownElement");
     testTag("big", "HTMLElement");
     testTag("blockquote", "HTMLQuoteElement");
     testTag("body", "HTMLBodyElement");

third_party/WebKit/Source/core/html/HTMLTagNames.in

@@ -17,7 +17,7 @@ base
 basefont interfaceName=HTMLElement
 bdi interfaceName=HTMLBDIElement, JSInterfaceName=HTMLElement
 bdo interfaceName=HTMLElement
-bgsound interfaceName=HTMLElement
+bgsound interfaceName=HTMLUnknownElement
 big interfaceName=HTMLElement
 blockquote interfaceName=HTMLQuoteElement
 body