Try to improve toolbar separator coloration for themed browser windows.

chrome/browser/themes/theme_properties.cc

Index: chrome/browser/themes/theme_properties.cc
diff --git a/chrome/browser/themes/theme_properties.cc b/chrome/browser/themes/theme_properties.cc
index 3d09033caeca19b76c4bdac6b3be178ee69dd30d..9203e1695c8c7f28461ed1b6d8f4874b180e4b54 100644
--- a/chrome/browser/themes/theme_properties.cc
+++ b/chrome/browser/themes/theme_properties.cc
@@ -84,9 +84,9 @@ constexpr color_utils::HSL kDefaultTintBackgroundTab = {-1, -1, 0.75};
 // Defaults for properties which are not stored in the browser theme pack.
 
 constexpr SkColor kDefaultColorControlBackground = SK_ColorWHITE;
-const SkColor kDefaultDetachedBookmarkBarSeparator =
+const SkColor kDefaultToolbarBottomSeparator =
     SkColorSetRGB(0xB6, 0xB4, 0xB6);
-const SkColor kDefaultDetachedBookmarkBarSeparatorIncognito =
+const SkColor kDefaultToolbarBottomSeparatorIncognito =
     SkColorSetRGB(0x28, 0x28, 0x28);
 const SkColor kDefaultToolbarTopSeparator = SkColorSetA(SK_ColorBLACK, 0x40);
 
@@ -270,13 +270,17 @@ SkColor ThemeProperties::GetDefaultColor(int id, bool otr) {
     case COLOR_BOOKMARK_BAR_INSTRUCTIONS_TEXT:
       return otr ? kDefaultColorBookmarkInstructionsTextIncognito
                  : kDefaultColorBookmarkInstructionsText;
-    case COLOR_TOOLBAR_BOTTOM_SEPARATOR:
     case COLOR_DETACHED_BOOKMARK_BAR_SEPARATOR:
-      return otr ? kDefaultDetachedBookmarkBarSeparatorIncognito
-                 : kDefaultDetachedBookmarkBarSeparator;
+      // We shouldn't reach this case because the color is calculated from
+      // COLOR_TOOLBAR_BOTTOM_SEPARTOR.
+      NOTREACHED();
+      return gfx::kPlaceholderColor;
     case COLOR_DETACHED_BOOKMARK_BAR_BACKGROUND:
       return otr ? kDefaultDetachedBookmarkBarBackgroundIncognito
                  : kDefaultDetachedBookmarkBarBackground;
+    case COLOR_TOOLBAR_BOTTOM_SEPARATOR:
+      return otr ? kDefaultToolbarBottomSeparatorIncognito
+                 : kDefaultToolbarBottomSeparator;
     case COLOR_TOOLBAR_TOP_SEPARATOR:
     case COLOR_TOOLBAR_TOP_SEPARATOR_INACTIVE:
       return kDefaultToolbarTopSeparator;