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This implements the various types of file inputs, which required a
few parts:

1) Intents sent from weblayer need to go through the fragment, not the
   activity, so we can handle the responses.
2) Copied file_select_helper.* from
   chrome/browser/file_select_helper.*, but greatly simplified them
   since we likely will not need much of that functionality.
3) Add a FileProvider, which is used when uploading image files from the
   camera.

Change-Id: Iaf01199de8fdd11fc89b2178f69e700794861eed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1873128Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708350}