Part of fix for bug 5523834, backporting cache fixes

This is hopefully a fix for bug 5255299

Cherry-picking CL
http://src.chromium.org/viewvc/chrome?view=rev&revision=103323

Did not cherry-pick the changes in
trunk/src/net/disk_cache/backend_unittest.cc
as we are not running the tests on Android.

Change-Id: I765b72d7c9e93e2a87aa5ad84ad62ca6ab38eac0
10 files changed