Attempt to fix a GCC build issue

unique_ptr in its header.

BUG=1026685

Change-Id: Iffeb041b8542bcbf40de29c7d3e0150bf887cedb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1934238
Auto-Submit: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718682}

third_party/blink/renderer/core/core_initializer.h

@@ -31,6 +31,8 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_CORE_INITIALIZER_H_
 #define THIRD_PARTY_BLINK_RENDERER_CORE_CORE_INITIALIZER_H_
 
+#include <memory>
+
 #include "base/macros.h"
 #include "third_party/blink/public/common/dom_storage/session_storage_namespace_id.h"
 #include "third_party/blink/renderer/core/core_export.h"