Implements a display scale tray setting behind a chrome switch

ui/display/display_unittest.cc

 // Copyright (c) 2012 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/display/display.h"
 
 #include "base/command_line.h"
 #include "base/test/scoped_command_line.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/display/display_switches.h"
@@ skipping 46 matching lines @@
   base::CommandLine* command_line = scoped_command_line.GetProcessCommandLine();
 
   Display::ResetForceDeviceScaleFactorForTesting();
 
   command_line->AppendSwitch(switches::kForceDeviceScaleFactor);
 
   EXPECT_EQ(1, Display::GetForcedDeviceScaleFactor());
   Display::ResetForceDeviceScaleFactorForTesting();
 }
 
+TEST(DisplayTest, ForcedDeviceScaleFactor) {
+  Display::SetForceDeviceScaleFactor(2);
+
+  EXPECT_EQ(2, Display::GetForcedDeviceScaleFactor());
+  Display::ResetForceDeviceScaleFactorForTesting();
+}
+
 TEST(DisplayTest, DisplayHDRValues) {
   base::test::ScopedCommandLine scoped_command_line;
   base::CommandLine* command_line = scoped_command_line.GetProcessCommandLine();
   {
     Display display;
     EXPECT_EQ(24, display.color_depth());
     EXPECT_EQ(8, display.depth_per_component());
   }
 
   command_line->AppendSwitch(switches::kEnableHDR);
   {
     Display display;
     EXPECT_EQ(48, display.color_depth());
     EXPECT_EQ(16, display.depth_per_component());
   }
 }
 
 }  // namespace display