Merge M49: Change Win32k PPAPI lockdown to use finch params for mime type.

BUG=523278

Review URL: https://codereview.chromium.org/1609133002

Cr-Commit-Position: refs/heads/master@{#371651}
(cherry picked from commit c91e967e98ace8db59aa9c29b0949603caa51050)

Review URL: https://codereview.chromium.org/1645143003 .

Cr-Commit-Position: refs/branch-heads/2623@{#179}
Cr-Branched-From: 92d77538a86529ca35f9220bd3cd512cbea1f086-refs/heads/master@{#369907}
7 files changed