windows opengl: Setup the OpenGL window size also on Windows.

Change-Id: I5020cfb86e02ac331cb8922397e8be4f7d68d15e
windows opengl: Don't construct WinSalGraphicsImpl just to destroy it again.

Change-Id: I61afb35503a3947aa21bd90224e2f8614033a384
windows opengl: Make SwapBuffers() actually do something.

Change-Id: If58e9eaccd4850d33302ced5e83f649415158e24