Add GetDisplayWithDisplayId to display::Screen.

blimp/engine/app/ui/blimp_screen_unittest.cc

 // Copyright 2016 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 "blimp/engine/app/ui/blimp_screen.h"
 
 #include <memory>
 #include <string>
 #include <vector>
 
@@ skipping 96 matching lines @@
       display::DisplayObserver::DISPLAY_METRIC_BOUNDS |
       display::DisplayObserver::DISPLAY_METRIC_WORK_AREA;
   EXPECT_CALL(observer1_,
               OnDisplayMetricsChanged(EqualsDisplay(display), changed_metrics));
 
   gfx::Size size1(100, 100);
   screen_->UpdateDisplayScaleAndSize(2.0f, size1);
   EXPECT_EQ(size1, screen_->GetPrimaryDisplay().GetSizeInPixel());
 }
 
+TEST_F(BlimpScreenTest, GetDisplayById) {
+  // display_ in BlimpScreen has id 1
+  display::Display display;
+  bool has_display1 = screen_->GetDisplayWithDisplayId(0, &display);
+  EXPECT_FALSE(has_display1);
+  bool has_display2 = screen_->GetDisplayWithDisplayId(1, &display);
+  EXPECT_TRUE(has_display2);
+  EXPECT_EQ(1, display.id());
+}
+
 }  // namespace
 }  // namespace engine
 }  // namespace blimp