White screen at content shell launch.

White screen at content shell launch.

White screen is caused due to failure of gl draw calls.
GPU was blacklisted for content_shell due to which context
provider creation failed. This resulted in creation of
software resources instead of GL resources, for which GL
draw calls stand invalid.

This commit ignores gpu blacklist for content_shell similar
to efl_webview_app and ubrowser on desktop.

Bug: http://107.108.218.239/bugzilla/show_bug.cgi?id=15626

Reviewed by: a1.gomes, g.czajkowski

Change-Id: I53444ce02e6005a7a5021dbd5e540dde9b0a382b
Signed-off-by: Chandan Padhi <c.padhi@samsung.com>