[Texmap][Qt] Enable TextureMapperGL in platforms where BGRA is not present

[Texmap][Qt] Enable TextureMapperGL in platforms where BGRA is not present
https://bugs.webkit.org/show_bug.cgi?id=65473

Reviewed by Andreas Kling.

For now, swap RGBA->BGRA in software if we're in OpenGL ES 2.
We do that by iterating on the pixels and manually swapping each pixel's red and blue
values. This can be done faster with shaders, but for now this is a working solution
for platforms without BGRA support.

No new tests. Existing layout tests cover this.

* platform/graphics/opengl/TextureMapperGL.cpp:
(WebCore::BitmapTextureGL::endPaint):
* platform/graphics/opengl/TextureMapperGL.h:
* platform/graphics/qt/TextureMapperQt.cpp:
(WebCore::RGBA32PremultimpliedBufferQt::swapRGB):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@95939 268f45cc-cd09-0410-ab3c-d52691b4dbfc