[LayoutNG] Make NGBlockNode::CopyFragmentDataToLayoutBoxForInlineChildren private

This patch changes
  NGBlockNode::CopyFragmentDataToLayoutBoxForInlineChildren
to a private member function from an anonymous function, so
that the planned changes to the function is easier to review.

No changes other than moving within the same .cc file.

TBR=eae@chromium.org

Bug: 636993
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: I8af2cd1872e9f6c66156368c508ea4f209fc3255
Reviewed-on: https://chromium-review.googlesource.com/1179491
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583997}
2 files changed