Move CollectInlinesInternal to anonymous namespace

This is a follow-up patch of crrev.com/2965573003, moving the local function
to the anonymous namespace.

BUG=699017
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_layout_ng

Review-Url: https://codereview.chromium.org/2962243002
Cr-Commit-Position: refs/heads/master@{#483828}
1 file changed