For background mode:
1. ProcessMemoryDump knows the level of detail.
2. It checks for dump name to be present in whitelist. If not then
   returns a dummy mad. The strings are stripped of numbers (ids) and
   checked against a whitelist of dump names.
3. Disable creating new dumps just to mark suballocations.
4. Disable creation of global allocator dumps.
5. Disable string attributes in allocator dumps.
Also creates a new whitelist file to handle whitelisting logic.

BUG=613198
TBR=shess@chromium.org, jochen@chromium.org

Review-Url: https://codereview.chromium.org/2006943003
Cr-Commit-Position: refs/heads/master@{#397918}