Chrome Empties: Add asset for Recent Tabs Other Devices.

This CL adds PDF assets for the empty state of the Other Devices section in the Recent Tabs TableView.
PDF assets will be used as vector images to display at big scale without impacting binary size.
These assets will have colour information, so there will be one version for dark mode and another one for any appearance.

(Googlers only links)
Design Doc: https://docs.google.com/document/d/1JM2sKT4oghkol51U7_3xv9sfaB26C89CCGa2uwYBgsI/edit?usp=sharing
UX Specs with mocks: https://docs.google.com/presentation/d/1x1lSTOSQ1zkJu87SoigiUhX2f9oHACglR22yYg-lSHo/edit?usp=sharing

Bug: 1098328
Change-Id: I396603d96ad72c7326f9652e884824c3f9e9b7fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2298054Reviewed-by: Sebastien Lalancette <seblalancette@chromium.org>
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Maxime Charland <mcharland@google.com>
Cr-Commit-Position: refs/heads/master@{#790116}

ios/chrome/browser/ui/recent_tabs/BUILD.gn

@@ -65,6 +65,7 @@ source_set("recent_tabs_ui") {
   ]
   deps = [
     ":recent_tabs_ui_constants",
+    "resources:recent_tabs_other_devices_empty",
     "//base",
     "//components/sessions",
     "//components/strings",

ios/chrome/browser/ui/recent_tabs/resources/BUILD.gn

@@ -4,6 +4,14 @@
 
 import("//build/config/ios/asset_catalog.gni")
 
+imageset("recent_tabs_other_devices_empty") {
+  sources = [
+    "recent_tabs_other_devices_empty.imageset/Contents.json",
+    "recent_tabs_other_devices_empty.imageset/recent_tabs_other_devices_empty.pdf",
+    "recent_tabs_other_devices_empty.imageset/recent_tabs_other_devices_empty_dark.pdf",
+  ]
+}
+
 imageset("show_history") {
   sources = [
     "show_history.imageset/Contents.json",

ios/chrome/browser/ui/recent_tabs/resources/recent_tabs_other_devices_empty.imageset/Contents.json

+{
+  "images" : [
+    {
+      "filename" : "recent_tabs_other_devices_empty.pdf",
+      "idiom" : "universal"
+    },
+    {
+      "appearances" : [
+        {
+          "appearance" : "luminosity",
+          "value" : "dark"
+        }
+      ],
+      "filename" : "recent_tabs_other_devices_empty_dark.pdf",
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  },
+  "properties" : {
+    "preserves-vector-representation" : true
+  }
+}