drive: Start change list loading and directory loading at the same time for initial load

On initial load, start change list loading and directory loading at the same time.
Avoid starting directory loading when change list loading is expected to finish quickly.

BUG=335469
TEST=unit_tests
R=kinaba@chromium.org

Review URL: https://codereview.chromium.org/171603013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252484 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252484
Telemetry: Use mimimum tracing for timeline benchmarks.

PERF SHERIFF WARNING: This will drastically change the 
thread-time benchmarks for the better. This is purely a
measurement change though, by removing overhead from traces.

Tracing adds significant overhead. We can add more details
by default as we prune the list of traces.

When details are reported, default traces are enabled again,
as otherwise there is no details to report.

BUG=331903

Review URL: https://codereview.chromium.org/171013006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252485 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252485