[BlobStorage] Enabling disk storage and paging.
Adds support for saving blobs to disk by either paging them to disk
or sending files directly to the renderer.
Note: Disk is turned off by default (limit=0). So other than tests
that explicitly set a higher disk limit, this patch should be a NOOP.
The next patch will configure this limit (and the current RAM limit)
by the OS, disk size, and available RAM.
R=michaeln,kinuko
BUG=375297
Committed: https://crrev.com/89bdfe0bd9499962f9f05c30a72d46fc6510d45a
Review-Url: https://codereview.chromium.org/2516713002
Cr-Original-Commit-Position: refs/heads/master@{#436415}
Cr-Commit-Position: refs/heads/master@{#436485}
19 files changed
