Third-party blocking means that shell extensions in the file picker dialog will no longer work. In some cases ( crbug.com/881670 ) this will be a good thing and will avoid hangs, but in other cases it will lead to reduced functionality - shell extensions for picking files from virtual folders hosted in the cloud will not work.

Another problem with the current file picker implementation is that it can lead to COM hangs such as  crbug.com/645913  and  http://crbug.com/759848 .

Running the file picker in a separate process that allows third-party injection will automatically give us support for selecting cloud-stored files. We will have to test to make sure that we can actually *do* anything with these files from the browser process.

There may be some existing code for hosting the file picker in a separate process.

Because of bugs like  crbug.com/881670  we should make sure that there is a consumer accessible way to disable this system (or block third-party injection in the child process). This should be hosted in chrome://flags/ and can be used by customers who report file-picker issues in order to rule out third-party interference.