Single ShareableBitmap revision blacks out WebView on Harmattan

Single ShareableBitmap revision blacks out WebView on Harmattan
https://bugs.webkit.org/show_bug.cgi?id=83631

When swizzling is not supported in the driver, we need to initialize the texture as RGBA,
and make sure that the manual swizzling only modifies the sub-image.

Rubber stamped by Kenneth Rohde Christiansen.

Covered by existing tests.

* platform/graphics/texmap/TextureMapperGL.cpp:
(WebCore::swizzleBGRAToRGBA):
(WebCore::BitmapTextureGL::didReset):
(WebCore):
(WebCore::BitmapTextureGL::updateContents):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@113873 268f45cc-cd09-0410-ab3c-d52691b4dbfc