Zoom lookup should use the correct dsf.

Bug: b/141898654
Test: updated the test to catch this type of regression
Change-Id: Icee3d5aeb825748333bbe7094f10124d0e61f59f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1951152
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Malay Keshav <malaykeshav@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721745}

ui/display/manager/display_util.cc

@@ -52,12 +52,14 @@ constexpr std::array<ZoomListBucket, 8> kZoomListBuckets{{
 constexpr std::array<ZoomListBucketDsf, 6> kZoomListBucketsForDsf{{
     {1.25f, {0.7f, 1.f / 1.25f, 0.85f, 0.9f, 0.95f, 1.f, 1.1f, 1.2f, 1.3f}},
     {1.6f, {1.f / 1.6f, 0.7f, 0.75f, 0.8f, 0.85f, 0.9f, 1.f, 1.15f, 1.3f}},
-    {1.77777f,
-     {1.f / 1.77777f, 0.65f, 0.75f, 0.8f, 0.9f, 1.f, 1.1f, 1.2f, 1.3f}},
+    {1.77777779102325439453125f,
+     {1.f / 1.77777779102325439453125f, 0.65f, 0.75f, 0.8f, 0.9f, 1.f, 1.1f,
+      1.2f, 1.3f}},
     {2.f, {1.f / 2.f, 0.6f, 0.7f, 0.8f, 0.9f, 1.f, 1.1f, 1.25f, 1.5f}},
     {2.25f, {1.f / 2.25f, 0.6f, 0.7f, 0.8f, 0.9f, 1.f, 1.15f, 1.3f, 1.5f}},
-    {2.66666f,
-     {1.f / 2.66666f, 0.5f, 0.6f, 0.8f, 0.9f, 1.f, 1.2f, 1.35f, 1.5f}},
+    {2.6666667461395263671875f,
+     {1.f / 2.6666667461395263671875f, 0.5f, 0.6f, 0.8f, 0.9f, 1.f, 1.2f, 1.35f,
+      1.5f}},
 }};
 
 bool WithinEpsilon(float a, float b) {

ui/display/manager/display_utils_unittest.cc

@@ -10,6 +10,7 @@
 #include "base/macros.h"
 #include "base/strings/stringprintf.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "ui/display/manager/display_change_observer.h"
 #include "ui/display/manager/managed_display_info.h"
 #include "ui/gfx/geometry/size.h"
 
@@ -56,11 +57,15 @@ TEST_F(DisplayUtilTest, DisplayZooms) {
   }
 }
 
-TEST_F(DisplayUtilTest, DisplayZoomsWithInternalDsf) {
-  std::vector<float> kDsfs = {1.25f, 1.6f, 1.77777f, 2.f, 2.25f, 2.66666f};
-
-  for (const auto& dsf : kDsfs) {
-    SCOPED_TRACE(base::StringPrintf("dsf=%f", dsf));
+TEST_F(DisplayUtilTest, DisplayZoomsWithInternal) {
+  std::vector<float> kDpis = {160, 200, 225, 240, 280, 320};
+  float previous_dsf = 0.f;
+  for (const auto& dpi : kDpis) {
+    SCOPED_TRACE(base::StringPrintf("dpi=%f", dpi));
+    float dsf = DisplayChangeObserver::FindDeviceScaleFactor(dpi);
+    // Make sure each dpis is mapped to different dsf.
+    EXPECT_NE(previous_dsf, dsf);
+    previous_dsf = dsf;
     const std::vector<float> zoom_values = GetDisplayZoomFactorForDsf(dsf);
     const float inverse_dsf = 1.f / dsf;
     uint8_t checks = 0;