[realbox] Updates grey color of realbox action buttons

Update color of the expand arrow button as well as the deletion button
from Grey 900 --> Grey 700.

before: screenshot/4mphygPwGNXtcDv
after: screenshot/6CSf8WmB8DXD9kW

Fixed: 1146256
Change-Id: Iaddb97e4f7b70b85ca61815a6f341896832ea32a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2547924
Commit-Queue: Moe Ahmadi <mahmadi@chromium.org>
Commit-Queue: Tibor Goldschwendt <tiborg@chromium.org>
Auto-Submit: Moe Ahmadi <mahmadi@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#828972}

chrome/browser/resources/new_tab_page/realbox_button.html

@@ -15,11 +15,11 @@
   }
 
   :host(:hover) {
-    background-color: var(--search-box-icon-bg-hovered, rgba(var(--google-grey-900-rgb), .16));
+    background-color: var(--search-box-icon-bg-hovered, rgba(var(--google-grey-refresh-700-rgb), .16));
   }
 
   :host(:focus-within) {
-    background-color: var(--search-box-icon-bg-focused, rgba(var(--google-grey-900-rgb), .32));
+    background-color: var(--search-box-icon-bg-focused, rgba(var(--google-grey-refresh-700-rgb), .32));
   }
 
   #icon {
@@ -34,7 +34,7 @@
   :host-context(.header) #icon {
     -webkit-mask-image: url(icons/chevron.svg);
     -webkit-transform: rotate(180deg);
-    background-color: var(--search-box-icon, var(--google-grey-900));
+    background-color: var(--search-box-icon, var(--google-grey-refresh-700));
   }
 
   :host-context(.header[group-is-hidden]) #icon {
@@ -42,12 +42,12 @@
   }
 
   :host-context(ntp-realbox-match:hover) #icon {
-    background-color: var(--search-box-icon, var(--google-grey-900));
+    background-color: var(--search-box-icon, var(--google-grey-refresh-700));
   }
 
   :host-context(ntp-realbox-match:-webkit-any(:focus-within, .selected)) #icon,
   :host-context(.header:focus-within) #icon {
-    background-color: var(--search-box-icon-selected, var(--google-grey-900));
+    background-color: var(--search-box-icon-selected, var(--google-grey-refresh-700));
   }
 </style>
 <div id="icon"></div>