Ensuring interception of stream get determined by plugin path before checking mime...

Ensuring interception of stream get determined by plugin path before checking mime type.

Earlier we are checking whether a extension with url that have mime type
should be intercepted as stream by checking plugin availablity.
Now we are passing plugin path and then checking whether their is
MimehandlerView Plugin available with that path and then we are allowing
intercepted as stream. So now interception is not depends upon mimetype.

BUG=443466

Review URL: https://codereview.chromium.org/953793003

Cr-Commit-Position: refs/heads/master@{#324187}