Get 'gn_all' building on iOS

components/sessions/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 if (is_android) {
   import("//build/config/android/config.gni")
 }
 
 config("implementation") {
   defines = [ "SESSIONS_IMPLEMENTATION" ]
@@ skipping 162 matching lines @@
     ]
   }
 
   public_deps = [
     ":sessions",
   ]
 
   deps = [
     ":test_support",
     "//base/test:test_support",
-    "//content/public/common",
     "//sync",
     "//testing/gtest",
     "//ui/base",  # For page transition types.
     "//url",
   ]
+
+  if (!is_ios) {
+    deps += [ "//content/public/common" ]
+  }
 }