Modifies the threshold for hidpi displays.

ui/display/display_util_unittest.cc

 // Copyright 2014 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_util.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace ui {
 
 TEST(DisplayUtilTest, TestBlackListedDisplay) {
   EXPECT_TRUE(IsDisplaySizeBlackListed(gfx::Size(10, 10)));
   EXPECT_TRUE(IsDisplaySizeBlackListed(gfx::Size(40, 30)));
   EXPECT_TRUE(IsDisplaySizeBlackListed(gfx::Size(50, 40)));
   EXPECT_TRUE(IsDisplaySizeBlackListed(gfx::Size(160, 90)));
   EXPECT_TRUE(IsDisplaySizeBlackListed(gfx::Size(160, 100)));
 
   EXPECT_FALSE(IsDisplaySizeBlackListed(gfx::Size(50, 60)));
   EXPECT_FALSE(IsDisplaySizeBlackListed(gfx::Size(100, 70)));
   EXPECT_FALSE(IsDisplaySizeBlackListed(gfx::Size(272, 181)));
 }
 
+TEST(DisplayUtilTest, GetScaleFactor) {
+  // Normal chromebook spec. DPI ~= 130
+  EXPECT_EQ(1.0f, GetScaleFactor(
+      gfx::Size(256, 144), gfx::Size(1366, 768)));
+
+  // HiDPI like Pixel. DPI ~= 240
+  EXPECT_EQ(2.0f, GetScaleFactor(
+      gfx::Size(272, 181), gfx::Size(2560, 1700)));
+
+  // A large external display but normal pixel density. DPI ~= 100
+  EXPECT_EQ(1.0f, GetScaleFactor(
+      gfx::Size(641, 400), gfx::Size(2560, 1600)));
+
+  // A large external display with high pixel density. DPI ~= 157
+  EXPECT_EQ(2.0f, GetScaleFactor(
+      gfx::Size(621, 341), gfx::Size(3840, 2160)));
+
+  // 4K resolution but the display is physically even larger. DPI ~= 114
+  EXPECT_EQ(1.0f, GetScaleFactor(
+      gfx::Size(854, 481), gfx::Size(3840, 2160)));
+
+  // 21.5 inch, 1080p. DPI ~= 102
+  EXPECT_EQ(1.0f, GetScaleFactor(
+      gfx::Size(476, 267), gfx::Size(1920, 1080)));
+
+  // Corner case; slightly higher density but smaller screens. DPI ~= 165
+  EXPECT_EQ(1.0f, GetScaleFactor(
+      gfx::Size(293, 165), gfx::Size(1920, 1080)));
+}
+
 }  // namespace ui