CompressionStreams: Free Vector in Flush()

Vector named out_buffer_ was not freed, so I added out_buffer_.clear()
in Flush.

Bug: 999091
Change-Id: Id3bb458a126d4df61f42a6c43113368a89fcb889
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1855058
Commit-Queue: Canon Mukai <canonmukai@google.com>
Reviewed-by: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704950}

third_party/blink/renderer/modules/compression/deflate_transformer.cc

@@ -79,6 +79,7 @@ void DeflateTransformer::Flush(
   Deflate(nullptr, 0u, IsFinished(true), controller, exception_state);
   was_flush_called_ = true;
   deflateEnd(&stream_);
+  out_buffer_.clear();
 }
 
 void DeflateTransformer::Deflate(

third_party/blink/renderer/modules/compression/inflate_transformer.cc

@@ -72,6 +72,7 @@ void InflateTransformer::Flush(
   Inflate(nullptr, 0u, IsFinished(true), controller, exception_state);
   inflateEnd(&stream_);
   was_flush_called_ = true;
+  out_buffer_.clear();
 }
 
 void InflateTransformer::Inflate(