Add GetDisplayWithDisplayId to display::Screen.

ui/views/widget/desktop_aura/desktop_screen_x11_unittest.cc

Index: ui/views/widget/desktop_aura/desktop_screen_x11_unittest.cc
diff --git a/ui/views/widget/desktop_aura/desktop_screen_x11_unittest.cc b/ui/views/widget/desktop_aura/desktop_screen_x11_unittest.cc
index 65fdeee7aa367274806508e13182465fa74e5f1a..031d11b2314ef97523d21d0e5501a9eafe362b66 100644
--- a/ui/views/widget/desktop_aura/desktop_screen_x11_unittest.cc
+++ b/ui/views/widget/desktop_aura/desktop_screen_x11_unittest.cc
@@ -213,6 +213,26 @@ TEST_F(DesktopScreenX11Test, RemoveMonitorOnLeft) {
   EXPECT_EQ(1u, removed_display_.size());
 }
 
+TEST_F(DesktopScreenX11Test, GetDisplayById) {

[sky, 2016/11/19 15:01:40]

Can you clarify why you need the same test for each platform? Aren't you
effectively testing the exact same implementation each time? By that I mean
Screen:GetDisplayWithDisplayId() is non-virtual, so isn't one test enough?

+  std::vector<display::Display> displays;
+  displays.push_back(
+      display::Display(kFirstDisplay, gfx::Rect(0, 0, 640, 480)));
+  displays.push_back(
+      display::Display(kSecondDisplay, gfx::Rect(640, 0, 1024, 768)));
+  NotifyDisplaysChanged(displays);
+
+  display::Display display1;
+  bool has_display1 =
+      screen()->GetDisplayWithDisplayId(kFirstDisplay, &display1);
+  display::Display display2;
+  bool has_display2 =
+      screen()->GetDisplayWithDisplayId(kSecondDisplay, &display2);
+  EXPECT_TRUE(has_display1);
+  EXPECT_TRUE(has_display2);
+  EXPECT_EQ(kFirstDisplay, display1.id());
+  EXPECT_EQ(kSecondDisplay, display2.id());
+}
+
 TEST_F(DesktopScreenX11Test, GetDisplayNearestPoint) {
   std::vector<display::Display> displays;
   displays.push_back(