M38 gardening: remove dependency on content_worker target.

CL: https://codereview.chromium.org/411283002
M38 gardening: Update pak locations.

CL: https://codereview.chromium.org/398873004
M38 gardening: Update pak location.

CL: https://codereview.chromium.org/381113004
M38 gardening: Fix another pak location.

CL: https://codereview.chromium.org/398243002
M38 gardening: Stop using base::Value::CreateStringValue().

CL: https://codereview.chromium.org/415423002