[Fuchsia] Fix DCHECK when destroying FuchsiaVideoDecoder.

FuchsiaVideoDecoder was crashing with a DCHECK in SendInputPacket()
while being destroyed  because in_flight_input_packets_ were cleared
while there is pending data in the queue, which was causing new input
packets to be produced. Added ReleaseInputBuffers() call in
~FuchsiaVideoDecoder() to avoid this issue.

Bug: 1013919
Change-Id: Id455e97ad8dad70d6aaa7dfc1bbee0426df7ae48
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1898777
Auto-Submit: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712661}

media/filters/fuchsia/fuchsia_video_decoder.cc

@@ -315,6 +315,11 @@ FuchsiaVideoDecoder::FuchsiaVideoDecoder(
 }
 
 FuchsiaVideoDecoder::~FuchsiaVideoDecoder() {
+  // Call ReleaseInputBuffers() to make sure the corresponding fields are
+  // destroyed in the right order.
+  ReleaseInputBuffers();
+
+  // Release mailboxes used for output frames.
   ReleaseOutputBuffers();
 }