Fix validity check in SkSurface::MakeFromBackendTextureAsRenderTarget

Swaped the order of validate_backend_texture() and
SkSurface_Gpu::Valid() so that the pixel config computed by
validate_backend_texture() get used by SkSurface_Gpu::Valid().
This makes the behavior of this method consistent with the behavior
of sister method MakeFromBackendTexture()

BUG=788439

Change-Id: I132ea8da23430ea99bbeabce79b08edb6b4cae03
Reviewed-on: https://skia-review.googlesource.com/141837
Commit-Queue: Justin Novosad <junov@chromium.org>
Reviewed-by: Justin Novosad <junov@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Auto-Submit: Justin Novosad <junov@chromium.org>
1 file changed