New context extensions restored improperly
https://bugs.webkit.org/show_bug.cgi?id=112156

Patch by Rajeev Sarvaria <rsarvaria@blackberry.com> on 2013-03-15
Reviewed by Rob Buis.

Sets up extensions after new context is created for restoration.
Previous extensions set up is lost when context is initially lost.

Cannot create a test as change is not visible from the web. When a context
is lost, WebGLRenderingContext drops m_context. Upon restoration a new context
object is created without available extensions initialized. Calling isEnabled
within setupFlags leads to the eventual initialization of extensions for the
new context.

* html/canvas/WebGLRenderingContext.cpp:
(WebCore):
(WebCore::WebGLRenderingContext::maybeRestoreContext):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145955 268f45cc-cd09-0410-ab3c-d52691b4dbfc