Enable plugin blocking for browser plugins.
This enables plugin blocking through content settings to function for
the out of process PDF extension. This CL changes
ChromeContentRendererClient to apply the same logic to browser plugins
as it does to other plugin types. To enable this, this CL also moves
the creation of browser plugins from RenderFrameImpl::createPlugin to
RenderFrameImpl::CreatePlugin. Browser plugins using the
"application/browser-plugin" MIME type (webview) are unaffected by this
change.
To avoid a nested blocked plugin, this also whitelists the PDF plugin
to always be allowed within the PDF extension.
BUG=454694
Review URL: https://codereview.chromium.org/
920303003
Cr-Commit-Position: refs/heads/master@{#316707}