media/gpu: Fix VaapiWrapper::DestroySurfaces() bug.

This CL fixes a bug in which, in some cases, empty vectors of type VASurfaceID
were passed to vaDestroySurfaces.

Bug: 973235
Test: jpeg_decode_accelerator_unittest
Change-Id: Ic285a71134e6030210ad794e4f74992ffb1965b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1655991
Commit-Queue: Gil Dekel <gildekel@chromium.org>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
Reviewed-by: Andres Calderon Jaramillo <andrescj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#668524}

media/gpu/vaapi/vaapi_wrapper.cc

@@ -1831,10 +1831,10 @@ bool VaapiWrapper::CreateSurfaces(unsigned int va_format,
 void VaapiWrapper::DestroySurfaces(std::vector<VASurfaceID> va_surfaces) {
   DVLOG(2) << "Destroying " << va_surfaces.size() << " surfaces";
 
-  if (va_surfaces.empty())
-    return;
   // vaDestroySurfaces() makes no guarantees about VA_INVALID_SURFACE.
   base::Erase(va_surfaces, VA_INVALID_SURFACE);
+  if (va_surfaces.empty())
+    return;
 
   base::AutoLock auto_lock(*va_lock_);
   const VAStatus va_res =