Fix running gn gen for //ui/* targets on iOS.

ui/events/BUILD.gn

Index: ui/events/BUILD.gn
diff --git a/ui/events/BUILD.gn b/ui/events/BUILD.gn
index b2d2ec7910f5795b0599050ed12f4a0ee4945183..a69b1d7056d6419b7ab3688e2f678cb8d28c59f8 100644
--- a/ui/events/BUILD.gn
+++ b/ui/events/BUILD.gn
@@ -333,13 +333,18 @@ test("events_unittests") {
     "//base/test:run_all_unittests",
     "//skia",
     "//testing/gtest",
-    "//third_party/WebKit/public:blink_headers",
     "//ui/events/devices",
-    "//ui/events/gestures/blink",
     "//ui/events/platform",
     "//ui/gfx:test_support",
   ]
 
+  if (!is_ios) {
+    deps += [
+      "//third_party/WebKit/public:blink_headers",
+      "//ui/events/gestures/blink",
+    ]
+  }
+
   include_dirs = [ "//testing/gmock/include" ]
 
   if (use_x11) {