[ios] Splits history_ui_constants into a separate GN target.

This will allow EG2 tests to use these constants without pulling in
more of //ios/chrome/browser/ui.

BUG=None

Change-Id: Ifb5dbeaf841b598767a63521aea6e07bb5f9dc4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1618123Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661377}

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

@@ -36,6 +36,14 @@ source_set("history") {
   ]
 }
 
+source_set("constants") {
+  configs += [ "//build/config/compiler:enable_arc" ]
+  sources = [
+    "history_ui_constants.h",
+    "history_ui_constants.mm",
+  ]
+}
+
 source_set("history_ui") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
@@ -54,12 +62,11 @@ source_set("history_ui") {
     "history_table_view_controller.mm",
     "history_transitioning_delegate.h",
     "history_transitioning_delegate.mm",
-    "history_ui_constants.h",
-    "history_ui_constants.mm",
     "history_util.h",
     "history_util.mm",
   ]
   deps = [
+    ":constants",
     "public",
     "resources:empty_history",
     "//base",
@@ -136,6 +143,7 @@ source_set("eg_tests") {
     "history_ui_egtest.mm",
   ]
   deps = [
+    ":constants",
     ":history",
     ":history_ui",
     "//base",

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

@@ -130,6 +130,7 @@ source_set("eg_tests") {
     "//ios/chrome/app/strings",
     "//ios/chrome/browser/tabs",
     "//ios/chrome/browser/ui/authentication:eg_test_support",
+    "//ios/chrome/browser/ui/history:constants",
     "//ios/chrome/browser/ui/history:history_ui",
     "//ios/chrome/browser/ui/table_view",
     "//ios/chrome/browser/ui/util",

ios/chrome/test/earl_grey/BUILD.gn

@@ -262,6 +262,7 @@ source_set("test_support") {
     "//ios/chrome/browser/ui/commands:commands",
     "//ios/chrome/browser/ui/content_suggestions:content_suggestions_constant",
     "//ios/chrome/browser/ui/content_suggestions:content_suggestions_ui",
+    "//ios/chrome/browser/ui/history:constants",
     "//ios/chrome/browser/ui/history:history_ui",
     "//ios/chrome/browser/ui/location_bar:location_bar",
     "//ios/chrome/browser/ui/omnibox:omnibox_internal",