GitLab

Default frame colors are changed so that inactive frames are always a
blend of 80% white/20% active color to increase contrast.
* The normal/inactive frame is changed to #F6F6F6 on all platforms. (OSX
  was already at this color.)
* The incognito/inactive frame is changed to #D4D5D5 on all platforms
  except OSX.
* The tints applied to theme images are changed to match the new
  lightness ratio as well. Inactive tint is changed to 80% lightness.
  Incognito/inactive is changed to be 74% lightness, which approximates
  blending 80% white on top of the active tint's 30% black. Also
  increased saturation change of incognito/inactive to match
  incognito/active.

Windows will now pick up the user colors specified by the system and use
them when custom drawing the titlebar. It will never draw the titlebar
white unless the user explicitly specifies that color. It uses an 80%
white/20% active blend to calculate inactive frame colors if the user
has no frame color specified, just like above.

BUG=505013,645682

Review-Url: https://codereview.chromium.org/2541873004
Cr-Commit-Position: refs/heads/master@{#439030}