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This CL implements a simple search that matches the functionality of the
original history page.

This CL also fixes a bug related to window separators in the synced view
that could cause excess window separators to appear.

BUG=610934
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2022003002
Cr-Commit-Position: refs/heads/master@{#398252}