Update the color of append, remove and bookmark icons.

The append and remove icons should be Google Grey 700 according to the
spec. Also update the color of bookmark icon to keep consistency.

Bug: 977265
Test: manually.

Change-Id: Iee48f612e4e3784480469c3f9fe237e7268fece4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1696531Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Meilin Wang <meilinw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676520}

chrome/browser/ui/app_list/search/omnibox_result.cc

@@ -31,8 +31,7 @@ namespace app_list {
 
 namespace {
 
-// #000 at 87% opacity.
-constexpr SkColor kListIconColor = SkColorSetARGB(0xDE, 0x00, 0x00, 0x00);
+constexpr SkColor kListIconColor = gfx::kGoogleGrey700;
 
 int ACMatchStyleToTagStyle(int styles) {
   int tag_styles = 0;