Fix header dependency in WebKit/public about testing

third_party/WebKit/public/BUILD.gn

Index: third_party/WebKit/public/BUILD.gn
diff --git a/third_party/WebKit/public/BUILD.gn b/third_party/WebKit/public/BUILD.gn
index ca750bb3d4f157e6f50918d8d80e5a304c03f1df..d63c9ab697fa43923630264d959e3ef0bb4e6c9d 100644
--- a/third_party/WebKit/public/BUILD.gn
+++ b/third_party/WebKit/public/BUILD.gn
@@ -27,6 +27,7 @@ group("blink") {
 group("test_support") {
   testonly = true
   public_deps = [
+    ":test_headers",
     "//third_party/WebKit/Source/platform:test_support",
     "//third_party/WebKit/Source/web:test_support",
   ]
@@ -86,6 +87,20 @@ if (is_android) {
   }
 }
 
+source_set("test_headers") {
+  testonly = true
+  sources = [
+    "platform/scheduler/test/fake_renderer_scheduler.h",
+    "platform/scheduler/test/mock_renderer_scheduler.h",
+    "platform/scheduler/test/renderer_scheduler_test_support.h",
+  ]
+  deps = [
+    "//base:base",
+    "//cc:cc",
+    "//testing/gmock:gmock",
+  ]
+}
+
 # Depend on this target to use public blink API headers for things like enums
 # and public structures without actually linking against any Blink libraries.
 source_set("blink_headers") {
@@ -430,9 +445,6 @@ source_set("blink_headers") {
     "platform/scheduler/child/webthread_base.h",
     "platform/scheduler/renderer/render_widget_scheduling_state.h",
     "platform/scheduler/renderer/renderer_scheduler.h",
-    "platform/scheduler/test/fake_renderer_scheduler.h",
-    "platform/scheduler/test/mock_renderer_scheduler.h",
-    "platform/scheduler/test/renderer_scheduler_test_support.h",
     "web/WebAXEnums.h",
     "web/WebAXObject.h",
     "web/WebActiveWheelFlingParameters.h",