media/gpu/vaapi/ScopedVAImage: reset(), not release(), ScopedVABufferMapping on destruction

ScopedVAImage release()s the unique_ptr of ScopedVABufferMapping on destruction.
However, release() doesn't execute ScopedVABufferMapping()'s dtor because it
just passes someone the ownership. We should call reset other than release.

Bug: 1018085
Test: camera.*JPEG
Change-Id: Ifc4b2133b33b2c7b0f08c899cb714881f9ffbaab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1880891
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
Auto-Submit: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709396}

media/gpu/vaapi/vaapi_utils.cc

@@ -103,7 +103,7 @@ ScopedVAImage::~ScopedVAImage() {
     base::AutoLock auto_lock(*lock_);
 
     // |va_buffer_| has to be deleted before vaDestroyImage().
-    va_buffer_.release();
+    va_buffer_.reset();
     vaDestroyImage(va_display_, image_->image_id);
   }
 }