Support double type parameterized feature policy

This allows us to specify value as following:

oversized-images *
equivalent to
oversized-images *(inf)

oversized-images 'self'
equivalent to
oversized-images 'self'(inf); <other-origin>(2.0)

Note that by default the allowed threshold is (2.0).
This aligns with current layout tests.

By default, oversized-images is enabled on * with value
inf.

Note that this CL does not update FP implementation of
oversized-images policy. It is separated into another
CL

BUG: 924568
Change-Id: I789f5e6f35561ab7c1472e73ad974787ed4aef3e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1480231
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Ian Clelland <iclelland@chromium.org>
Commit-Queue: Luna Lu <loonybear@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637776}
19 files changed