[omnibox] Lighten dimmed URL text in Refresh to GG600 per spec

The URL path, parameters, etc. (LOCATION_BAR_TEXT_DIMMED)
were being lightened to GG700 but now get GG600 per spec.
The RESULTS_ICON and RESULTS_TEXT_DIMMED using the same
colors remain intact.

Bug: 863474
Change-Id: I1dc2efb763642d88cbc27d832b0411a10c3310c8
Reviewed-on: https://chromium-review.googlesource.com/1141294
Commit-Queue: Orin Jaworski <orinj@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575916}

chrome/browser/ui/omnibox/omnibox_theme.cc

@@ -249,6 +249,7 @@ SkColor GetOmniboxColor(OmniboxPart part,
       return dark ? gfx::kGoogleGrey100 : gfx::kGoogleGrey900;
 
     case OmniboxPart::LOCATION_BAR_TEXT_DIMMED:
+      return dark ? gfx::kGoogleGrey500 : gfx::kGoogleGrey600;
     case OmniboxPart::RESULTS_ICON:
     case OmniboxPart::RESULTS_TEXT_DIMMED:
       // This is a pre-lightened (or darkened) variant of the base text color.