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}
7 files changed
