Limit PDF helper extension to print preview only

Limit PDF helper extension to print preview only

These days, the helper extension is only used by the print preview.
So make sure that the helper extension is only activated in print
previews and fall back to the standard MimeHandler otherwise.
When the helper extension is unexpectedly loaded directly instead
of through the mime handler, the extension will fail to initialize.
This is totally desired!

BUG=654280
TEST=See bug report, also confirmed that print preview still works.
R=thestig@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2407713002
Cr-Commit-Position: refs/heads/master@{#425280}
(cherry picked from commit c72f59f36a16c0cb64e0eebfc0999a09250740f0)

Committed: https://chromium.googlesource.com/chromium/src/+/37efdf4c7fdae4c604ad0b71781c36182b1517f0

[robwu, 2016-10-17 12:01:52]

Description was changed from

==========
Limit PDF helper extension to print preview only

These days, the helper extension is only used by the print preview.
So make sure that the helper extension is only activated in print
previews and fall back to the standard MimeHandler otherwise.
When the helper extension is unexpectedly loaded directly instead
of through the mime handler, the extension will fail to initialize.
This is totally desired!

BUG=654280
TEST=See bug report, also confirmed that print preview still works.
R=thestig@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2407713002
Cr-Commit-Position: refs/heads/master@{#425280}
(cherry picked from commit c72f59f36a16c0cb64e0eebfc0999a09250740f0)
==========

to

==========
Limit PDF helper extension to print preview only

These days, the helper extension is only used by the print preview.
So make sure that the helper extension is only activated in print
previews and fall back to the standard MimeHandler otherwise.
When the helper extension is unexpectedly loaded directly instead
of through the mime handler, the extension will fail to initialize.
This is totally desired!

BUG=654280
TEST=See bug report, also confirmed that print preview still works.
R=thestig@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2407713002
Cr-Commit-Position: refs/heads/master@{#425280}
(cherry picked from commit c72f59f36a16c0cb64e0eebfc0999a09250740f0)

Committed:
https://chromium.googlesource.com/chromium/src/+/37efdf4c7fdae4c604ad0b71781c...
==========

[robwu, 2016-10-17 12:01:54]

Committed patchset #1 (id:1) manually as
37efdf4c7fdae4c604ad0b71781c36182b1517f0.

[Lei Zhang, 2016-10-17 22:05:37]

lgtm