Windows Dark Mode: Update inactive tint to avoid hue shift

Bug: 1052427

This follows up http://crrev.com/c/1941064. The hue shift, with certain
accent colors could cause unexpected changes like a red accent titlebar
turning to blue when inactive. This change is to remove the hue shift
so the color overall stays in the same space but to still maintain as
close to the kGoogleGrey900 (0x20, 0x21, 0x24) ->
kGoogleGrey800 (0x3C, 0x40, 0x43) as possible.

With kGoogleGrey900 as the input, this code outputs (0x3B, 0x3E, 0x44).
I chose this one because it was very close to (0x3C, 0x40, 0x43) and kept
the overall color biased towards the green and blue channels.

Some other options considered were:
return {-1, 0.53, 0.567};  #3C3E43
return {-1, -1, 0.57};  #3F4043
return {-1, -1, 0.569};  #3F4042
return {-1, -1, 0.572};  #404144
return {-1, -1, 0.568};  #3E3F42
return {-1, 0.55, 0.567};  #3B3D44
return {-1, 0.54, 0.567};  #3B3E44
return {-1, 0.54, 0.57};  #3D3F45

Boosting the red channel and losing the green were resulting in
slightly warm and faded colors that didn't feel like they fit in the
Chromium color set.

Tested against the default Windows set of accent colors and saw
differentiation between active and inactive windows without unexpected
color shifts.

As a note on existing behavior, the colors of the new tab button and
background tab text can switch between active/inactive window states.

Change-Id: Ib67d11c720c58036cb255aee743916d6a8f2bab9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2063737
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742803}

chrome/browser/themes/theme_properties.cc

@@ -267,11 +267,12 @@ color_utils::HSL ThemeProperties::GetDefaultTint(int id,
     return {-1, 0.7, 0.075};  // #DEE1E6 -> kGoogleGrey900
   if (id == TINT_FRAME_INACTIVE) {
     // |dark_mode| is only true here when attempting to tint the Windows native
-    // frame color while in dark mode.  The goal in this case is to match the
-    // difference between Chrome default dark mode active and inactive frames,
-    // so return a shift that matches that.
+    // frame color while in dark mode when using OS accent titlebar colors.
+    // The goal in this case is to match the difference between Chrome default
+    // dark mode active and inactive frames as closely as possible without
+    // a hue change.
     if (dark_mode)
-      return {0.59, 0.53, 0.567};  // kGoogleGrey900 -> kGoogleGrey800
+      return {-1, 0.54, 0.567};  // Roughly kGoogleGrey900 -> kGoogleGrey800
 
     if (incognito)
       return {0.57, 0.65, 0.1405};  // #DEE1E6 -> kGoogleGrey800