Simplify security icon downgrade logic

Ignore mixed content that has the NONE state, since it will have the
WARNING state in M80. There is also no need to check secure schemes
in WARNING since the ones that shouldn't be warned will have the NONE
state.

This also fixes the issue where the icon shouldn't be downgraded when
the URL is loading (and has the NONE state).

[email protected],[email protected],[email protected]

(cherry picked from commit 0ca925ea185092e74260285825db738dc4223614)

Bug: 1031532
Change-Id: I167e74966cdd9dc7eb368209f481c24b9661c139
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1962801
Reviewed-by: Emily Stark <[email protected]>
Reviewed-by: Tommy Li <[email protected]>
Reviewed-by: Andrey Kosyakov <[email protected]>
Reviewed-by: Michael Thiessen <[email protected]>
Reviewed-by: Rohit Rao <[email protected]>
Commit-Queue: Livvie Lin <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#725212}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1972462
Reviewed-by: Livvie Lin <[email protected]>
Cr-Commit-Position: refs/branch-heads/3987@{#227}
Cr-Branched-From: c4e8da9871cc266be74481e212f3a5252972509d-refs/heads/master@{#722274}
18 files changed