[Extensions] Reduce the pixel threshold for icon visibility.

In IsRenderedIconSufficientlyVisible(), we render an icon against the
background toolbar color and check the resulting pixel RGB values
against a threshold. The current threshold results in over 70% of
icons declared in manifests being considered not visible.

Bug: 805600
Change-Id: Ie45b2e523d152fddebffdedd28749a05684c7fe7
Reviewed-on: https://chromium-review.googlesource.com/c/1407908
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: David Bertoni <dbertoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622248}
1 file changed