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- AnswerCardWebContents uses RemoteViewProvider to prepare answer card
  contents for embedding;
- SearchResultAnswerCardView uses RemoteViewHost to embed the
  contents from AnserCardWebContents;

Bug: 812434
Change-Id: I2c9785c96987367a72278c66205f20e579bf91ca
Reviewed-on: https://chromium-review.googlesource.com/992361
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548835}