Add GetDisplayWithDisplayId to display::Screen.

ui/views/widget/desktop_aura/desktop_screen_x11_unittest.cc

 // Copyright (c) 2013 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.
 
 #include "ui/views/widget/desktop_aura/desktop_screen_x11.h"
 
 #include <stdint.h>
 
 #include <memory>
 
@@ skipping 195 matching lines @@
   displays.clear();
   displays.push_back(
       display::Display(kSecondDisplay, gfx::Rect(0, 0, 1024, 768)));
   NotifyDisplaysChanged(displays);
 
   EXPECT_EQ(1u, changed_display_.size());
   EXPECT_EQ(0u, added_display_.size());
   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(
       display::Display(kFirstDisplay, gfx::Rect(0, 0, 640, 480)));
   displays.push_back(
       display::Display(kSecondDisplay, gfx::Rect(640, 0, 1024, 768)));
   NotifyDisplaysChanged(displays);
 
   EXPECT_EQ(kFirstDisplay,
             screen()->GetDisplayNearestPoint(gfx::Point(630, 10)).id());
@@ skipping 256 matching lines @@
   EXPECT_EQ(2u, changed_display_.size());
 
   displays[0].set_device_scale_factor(1.f);
   displays[1].set_device_scale_factor(1.f);
   NotifyDisplaysChanged(displays);
   EXPECT_EQ(4u, changed_display_.size());
   EXPECT_EQ(1.f, gfx::GetFontRenderParamsDeviceScaleFactor());
 }
 
 }  // namespace views