GCC: do not std::move unique ptr of forward declared UrlIndex

GCC fails to resolve the size of UrlIndex, needed
for moving a std::unique_ptr of UrlIndex. This is because
moved is done on a forward-declared UrlIndex.

To avoid the problem, move the call to std::move to the .cc
file so the full declaration is available.

Build error:
../../buildtools/third_party/libc++/trunk/include/memory: In instantiation of ‘void std::__1::default_delete<_Tp>::operator()(_Tp*) const [with _Tp = bookmarks::UrlIndex]’:
../../buildtools/third_party/libc++/trunk/include/memory:2634:22:   required from ‘void std::__1::unique_ptr<_Tp, _Dp>::reset(std::__1::unique_ptr<_Tp, _Dp>::pointer) [with _Tp = bookmarks::UrlIndex; _Dp = std::__1::default_delete<bookmarks::UrlIndex>; std::__1::unique_ptr<_Tp, _Dp>::pointer = bookmarks::UrlIndex*]’
../../buildtools/third_party/libc++/trunk/include/memory:2588:24:   required from ‘std::__1::unique_ptr<_Tp, _Dp>::~unique_ptr() [with _Tp = bookmarks::UrlIndex; _Dp = std::__1::default_delete<bookmarks::UrlIndex>]’
../../components/bookmarks/browser/bookmark_storage.h:107:76:   required from here
../../buildtools/third_party/libc++/trunk/include/memory:2317:25: error: invalid application of ‘sizeof’ to incomplete type ‘bookmarks::UrlIndex’
     static_assert(sizeof(_Tp) > 0,

Bug: 819294
Change-Id: I793a807c28e797aaa2e31d9c8b7e09fb6ca6b9e7
Reviewed-on: https://chromium-review.googlesource.com/1071648
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#562446}
2 files changed