Add SafeArchiveAnalyzer mojom service used to inspect ZIP / DMG
file archives for safe browsing download protection. Expose the
mojo to the browser via the utility process policy file. Update
clients to call the service using a mojo utility client, remove
all dependencies on UtilityProcessHostClient. Add native traits
for the file analyze results.

Align the ZIP/DMG clients: make their API's match, remove class
base::File fields (curry the file(s) to the analyzer step), and
remove ZIP client temp file clean-up code (not needed since the
utility process now owns the files).

Covered by existing tests:

SandboxedDMGAnalyzerTest.AnalyzeDMG, SandboxedZipAnalyzerTest.*

both of which use a content::InProcessUtilityThreadHelper viz.,
SafeArchiveAnalyzer mojo is called by these tests.

BUG=597124

Review-Url: https://codereview.chromium.org/2737763002
Cr-Commit-Position: refs/heads/master@{#456255}