[iOS][DarkMode] Support dark color in separator

Creates a local colorset for the separator.

Bug: 976645
Change-Id: I8e5168c18fe01095537c4d34cdba151db11f2d37
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1735162Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#684263}

ios/chrome/browser/ui/popup_menu/public/cells/BUILD.gn

@@ -10,6 +10,7 @@ source_set("cells") {
     "popup_menu_item.h",
   ]
   deps = [
+    "resources:popup_menu_separator_color",
     "//ios/chrome/browser/ui/table_view/cells",
   ]
   libs = [ "UIKit.framework" ]

ios/chrome/browser/ui/popup_menu/public/cells/popup_menu_footer_item.mm

@@ -42,7 +42,8 @@ const CGFloat kSeparatorMargin = 12;
   if (self) {
     UIView* separator = [[UIView alloc] init];
     separator.translatesAutoresizingMaskIntoConstraints = NO;
-    separator.backgroundColor = [UIColor colorWithWhite:0 alpha:0.05];
+    separator.backgroundColor =
+        [UIColor colorNamed:@"popup_menu_separator_color"];
     [self.contentView addSubview:separator];
     [NSLayoutConstraint activateConstraints:@[
       [separator.heightAnchor constraintEqualToConstant:kSeparatorHeight],

ios/chrome/browser/ui/popup_menu/public/cells/resources/BUILD.gn

+# Copyright 2017 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/config/ios/asset_catalog.gni")
+
+colorset("popup_menu_separator_color") {
+  sources = [
+    "popup_menu_separator_color.colorset/Contents.json",
+  ]
+}

ios/chrome/browser/ui/popup_menu/public/cells/resources/popup_menu_separator_color.colorset/Contents.json

+{
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  },
+  "colors" : [
+    {
+      "idiom" : "universal",
+      "color" : {
+        "color-space" : "display-p3",
+        "components" : {
+          "red" : "0xE8",
+          "alpha" : "1.000",
+          "blue" : "0xEC",
+          "green" : "0xEA"
+        }
+      }
+    },
+    {
+      "idiom" : "universal",
+      "appearances" : [
+        {
+          "appearance" : "luminosity",
+          "value" : "dark"
+        }
+      ],
+      "color" : {
+        "color-space" : "display-p3",
+        "components" : {
+          "red" : "0x47",
+          "alpha" : "1.000",
+          "blue" : "0x50",
+          "green" : "0x4C"
+        }
+      }
+    }
+  ]
+}
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