cb: depend on //base for unexpire_flags_gen

Bug: None
Change-Id: I5cdc27a89236b163d232f2f8360147ded353f796
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2154858
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760183}

chrome/browser/BUILD.gn

@@ -5739,7 +5739,10 @@ action("unexpire_flags_gen") {
 }
 
 source_set("unexpire_flags") {
-  deps = [ ":unexpire_flags_gen" ]
+  deps = [
+    ":unexpire_flags_gen",
+    "//base",
+  ]
   sources = [
     "$root_gen_dir/chrome/browser/unexpire_flags_gen.cc",
     "$root_gen_dir/chrome/browser/unexpire_flags_gen.h",