Note that this will probably affect a lot of things, e.g. tab divider color, so if we're going to do it (which I think we should), we need to do it reasonably soon to shake out bugs.

Therefore I'm upgrading to P1.

 Issue 848589  has been merged into this issue.

Note: This also means the midpoint calculation here (to decide which way to blend) should shift to be based on white vs. GG900, not white vs. black.

This should also be done in luminance rather than luma, since the former is what's used to actually calculate contrast.  See  bug 659451 .

So really what we probably want is: for all modes, change IsDark() to use luminance rather than luma and rename BlendTowardOppositeLuma() ( bug 659451 ); for refresh, change IsDark() and BlendTowardOppositeLuma() to calculate the dark point based on GG900 instead of black.

This just became a bit more complicated. BlendTowardOppositeLuma() lives in ui/gfx, which has no access to the Material Design Controller in ui/base.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ecc2df2b2d780cd591153862177365e47aced118

commit ecc2df2b2d780cd591153862177365e47aced118
Author: Robert Liao <robliao@chromium.org>
Date: Tue Jun 12 21:44:43 2018

Set the color_utils Darkest Color to gfx::kGoogleGrey900 for Material Refresh

BUG= 841271 

Change-Id: I39556cc73d4aa9705eed1d63e07a6e8a2c8eb726
Reviewed-on: https://chromium-review.googlesource.com/1095560
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566584}
[modify] https://crrev.com/ecc2df2b2d780cd591153862177365e47aced118/ui/base/material_design/material_design_controller.cc
[modify] https://crrev.com/ecc2df2b2d780cd591153862177365e47aced118/ui/gfx/color_utils.cc
[modify] https://crrev.com/ecc2df2b2d780cd591153862177365e47aced118/ui/gfx/color_utils.h
[modify] https://crrev.com/ecc2df2b2d780cd591153862177365e47aced118/ui/gfx/color_utils_unittest.cc