Merge to M57: Remove popup overlay from MHTML when requested

Merge to M57: Remove popup overlay from MHTML when requested

If the page is being loaded in background mode and saved to MHTML,
we should try to remove popup overlay that obstructs viewing the
normal content. This is controlled by MHTMLGenerationParams::
remove_popup_overlay.

BUG=684091
TEST=new tests added

Review-Url: https://codereview.chromium.org/2640923003
Cr-Commit-Position: refs/heads/master@{#445612}
(cherry picked from commit ec72fc4b04c800b1d54063d09b79350fdcd0cc15)

Review-Url: https://codereview.chromium.org/2656713002 .
Cr-Commit-Position: refs/branch-heads/2987@{#75}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/dd7ad8044610e0c92d8cc3695c19bf78ec3013ce

[jianli, 2017-01-24 22:07:59]

Description was changed from

==========
Merge to M57: Remove popup overlay from MHTML when requested

If the page is being loaded in background mode and saved to MHTML,
we should try to remove popup overlay that obstructs viewing the
normal content. This is controlled by MHTMLGenerationParams::
remove_popup_overlay.

BUG=684091
TEST=new tests added

Review-Url: https://codereview.chromium.org/2640923003
Cr-Commit-Position: refs/heads/master@{#445612}
(cherry picked from commit ec72fc4b04c800b1d54063d09b79350fdcd0cc15)
==========

to

==========
Merge to M57: Remove popup overlay from MHTML when requested

If the page is being loaded in background mode and saved to MHTML,
we should try to remove popup overlay that obstructs viewing the
normal content. This is controlled by MHTMLGenerationParams::
remove_popup_overlay.

BUG=684091
TEST=new tests added

Review-Url: https://codereview.chromium.org/2640923003
Cr-Commit-Position: refs/heads/master@{#445612}
(cherry picked from commit ec72fc4b04c800b1d54063d09b79350fdcd0cc15)

Review-Url: https://codereview.chromium.org/2656713002 .
Cr-Commit-Position: refs/branch-heads/2987@{#75}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/dd7ad8044610e0c92d8cc3695c19...
==========

[jianli, 2017-01-24 22:08:01]

Committed patchset #1 (id:1) manually as
dd7ad8044610e0c92d8cc3695c19bf78ec3013ce.