PDF Viewer - Search results don't work after rotating pdf

Currently search results are cleared when user rotates
pdf document. As a result, the forward/backward buttons in
find bar do not work if user rotates pdf document after
finding some text in the document.

This happens because |find_results_| is cleared in the method
InvalidateAllPages(), which is called after rotation.

This patch introduces a new method to restore find results state
after invalidate operation is done. New find operation is done
to ensure rects are correctly identified for search results and
correct region is highlighted on pressing forward/backward buttons
in find bar.

BUG=389782

Review URL: https://codereview.chromium.org/555803002

Cr-Commit-Position: refs/heads/master@{#298083}
2 files changed