convert //gpu to std::unique_ptr

BUG=554298
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_optional_gpu_tests_rel;tryserver.chromium.mac:mac_optional_gpu_tests_rel
TBR=danakj@chromium.org

Review URL: https://codereview.chromium.org/1859703002

Cr-Commit-Position: refs/heads/master@{#388176}

diff --git a/content/common/gpu/media/vp9_decoder.cc b/content/common/gpu/media/vp9_decoder.cc
index 1cb0dff..cba92fd 100644
--- a/content/common/gpu/media/vp9_decoder.cc
+++ b/content/common/gpu/media/vp9_decoder.cc

@@ -2,8 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/logging.h"
 #include "content/common/gpu/media/vp9_decoder.h"
+
+#include <memory>
+
+#include "base/logging.h"
 #include "media/base/limits.h"
 
 namespace content {