Added a quick heuristic to determine which objects are the target of in-page links and stop ignoring them for purposes of accessibility.

Windows screen readers were getting confused if the object to which an in-page link scrolled to was not an actual link target.
BUG=37721
R=dmazzoni@chromium.org
TESTED=manual testing with file attached to bug
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2713193003
Cr-Commit-Position: refs/heads/master@{#461530}
27 files changed