Revert "Make ~SurfaceTextureGLOwner check for null Surface."

This reverts commit f4c20b08.

Now that gles2_cmd_decoder deletes the group before |surface_|, we
shouldn't need to handle this case.

Bug: 718117
Change-Id: Ia2808674fc91d7b1d43525397d6e598f483d0909
Reviewed-on: https://chromium-review.googlesource.com/576060Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487584}

media/gpu/surface_texture_gl_owner.cc

@@ -73,12 +73,6 @@ SurfaceTextureGLOwnerImpl::~SurfaceTextureGLOwnerImpl() {
   // Make sure that the SurfaceTexture isn't using the GL objects.
   surface_texture_ = nullptr;
 
-  if (gl::GLSurface::GetCurrent() == nullptr) {
-    // This happens during GpuCommandBufferStub teardown.  Just leave -- the gpu
-    // process is going away.  crbug.com/718117 .
-    return;
-  }
-
   ui::ScopedMakeCurrent scoped_make_current(context_.get(), surface_.get());
   if (scoped_make_current.Succeeded()) {
     glDeleteTextures(1, &texture_id_);