Fixes omnibox text selection color.

[mkarolin]

Fixes brave/brave-browser#15690

Due to the cr91 upstream change below the omnibox selection color is
now the same color as the focus ring of the omnibox. Since we override
the focus ring to be our brand color, the selection is now also the
brand color, which we don't want.

This fix reverts the omnibox selection color to what it was in cr90
(kGoogleBlue200 for Light theme, kGoogleBlue800 for Dark).

Also, see a follow up issue brave/brave-browser#15732

Chromium changes:

This change redefined kColorId_TextfieldSelectionBackgroundFocused from
explicit colors (gfx::kGoogleBlue200 and gfx::kGoogleBlue800 ) to fall
back onto kColorId_LabelTextSelectionBackgroundFocused.

https://source.chromium.org/chromium/chromium/src/+/76f9ef872febca7e3630db31c699ad2c2ec4e7a5

commit 76f9ef872febca7e3630db31c699ad2c2ec4e7a5
Author: Peter Kasting [email protected]
Date: Mon Feb 22 17:56:22 2021 +0000

Convert existing color definitions to more canonical forms.

This defines as many colors as possible in terms of a small number of
core colors.  The primary benefit of this is to remove most dark mode
color definitions (which will now be automatically correct).  It also
makes some relationships clearer.

No behavior change intended (yet).

Bug: none

This change made kColorId_LabelTextSelectionBackgroundFocused fall back to
AlphaBlend(kColorId_ProminentButtonColor, kColorId_WindowBackground, gfx::kGoogleGreyAlpha500)
We redefine kColorId_ProminentButtonColor as kBraveColorBrand = RGB(0xfb, 0x54, 0x2b).

https://source.chromium.org/chromium/chromium/src/+/c042fff0a7823aa4ebb0494d5b094f67f15aa4b3

commit c042fff0a7823aa4ebb0494d5b094f67f15aa4b3
Author: Peter Kasting [email protected]
Date: Wed Mar 24 21:10:08 2021 +0000

Tweak existing systematized colors.

Primarily, this adjusts menus, tables, trees, and textfields to all use
the same blue to represent a selected item (and that blue now matches
the focus ring).

Bug: 1061127

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally: npm run test -- brave_browser_tests, npm run test -- brave_unit_tests, npm run lint, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan: