Fix MimeHandlerView plugin loading for data: URLs
MimeHandlerView plugins are passed access to the URL data by intercepting
the stream (in buffered_resource_handler.cc). This means that all URL
requests for these plugins need to go via the browser, otherwise they
won't be correctly intercepted. WebURLRequests for data: URLs have a fast
path for being loaded in the renderer which cannot be taken in the case
of loading these URLs.
BUG=477866
Review URL: https://codereview.chromium.org/
1091253004
Cr-Commit-Position: refs/heads/master@{#326421}