Add scarlet's panel in the test

Handle the edge case correctly to match ppi spec.
Added test to verify.

Bug: none
Change-Id: Ia32dc88d535446a593131a6237b6bbd47ed6edd8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2107237Reviewed-by: Malay Keshav <malaykeshav@chromium.org>
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#751445}

ui/display/manager/display_change_observer.cc

@@ -420,7 +420,7 @@ ManagedDisplayInfo DisplayChangeObserver::CreateManagedDisplayInfo(
 // static
 float DisplayChangeObserver::FindDeviceScaleFactor(float dpi) {
   for (size_t i = 0; i < base::size(kThresholdTableForInternal); ++i) {
-    if (dpi > kThresholdTableForInternal[i].dpi)
+    if (dpi >= kThresholdTableForInternal[i].dpi)
       return kThresholdTableForInternal[i].device_scale_factor;
   }
   return 1.0f;

ui/display/manager/display_change_observer_unittest.cc

@@ -195,6 +195,13 @@ TEST_P(DisplayChangeObserverTest, GetEmptyExternalManagedDisplayModeList) {
 }
 
 TEST_P(DisplayChangeObserverTest, FindDeviceScaleFactor) {
+  // sanity check
+  EXPECT_EQ(1.25f, DisplayChangeObserver::FindDeviceScaleFactor(150));
+  EXPECT_EQ(1.6f, DisplayChangeObserver::FindDeviceScaleFactor(180));
+  EXPECT_EQ(kDsf_1_777, DisplayChangeObserver::FindDeviceScaleFactor(220));
+  EXPECT_EQ(2.f, DisplayChangeObserver::FindDeviceScaleFactor(230));
+  EXPECT_EQ(kDsf_2_252, DisplayChangeObserver::FindDeviceScaleFactor(270));
+  EXPECT_EQ(kDsf_2_666, DisplayChangeObserver::FindDeviceScaleFactor(300));
   constexpr struct Data {
     const float diagonal_size;
     const gfx::Size resolution;
@@ -212,6 +219,7 @@ TEST_P(DisplayChangeObserverTest, FindDeviceScaleFactor) {
       {14.0f,  {1920, 1080}, 1.25f,      {1536, 864},  false},
       {11.6f,  {1920, 1080}, 1.6f,       {1200, 675},  false},
       {12.02f, {2160, 1440}, 1.6f,       {1350, 900},  false},
+      {9.7f,   {1536, 2048}, 2.0f,       {768, 1024},  false},
       {12.85f, {2560, 1700}, 2.0f,       {1280, 850},  false},
       {12.3f,  {2400, 1600}, 2.0f,       {1200, 800},  false},
       {10.1f,  {1920, 1200}, kDsf_1_777, {1080, 675},  false},