Add GetDisplayWithDisplayId to display::Screen.

extensions/browser/api/system_display/system_display_apitest.cc

Index: extensions/browser/api/system_display/system_display_apitest.cc
diff --git a/extensions/browser/api/system_display/system_display_apitest.cc b/extensions/browser/api/system_display/system_display_apitest.cc
index deeb22946080ade2963ecb95004e99156f332142..71f4d7f44c42d12870e653280c324cc4830ba5a5 100644
--- a/extensions/browser/api/system_display/system_display_apitest.cc
+++ b/extensions/browser/api/system_display/system_display_apitest.cc
@@ -50,6 +50,16 @@ class MockScreen : public Screen {
   std::vector<display::Display> GetAllDisplays() const override {
     return displays_;
   }
+  bool GetDisplayWithDisplayId(int64_t display_id,
+                               display::Display* display) const override {
+    for (display::Display display_in_list : displays_) {
+      if (display_in_list.id() == display_id) {
+        *display = display_in_list;
+        return true;
+      }
+    }
+    return false;
+  }
   display::Display GetDisplayNearestWindow(
       gfx::NativeView window) const override {
     return display::Display(0);