Disable subpixel positioning on chrome os

Subpixel positioning was needed because text layout was performed at 1x
device scale factor and then rastered to the final display device scale
factor leading to glyph artifacts and inconsistent glyph positioning.
With pixel canvas enabled on chrome os, the text layout is now always
performed at the final display device scale factor. This, coupled with
the replacement of ui scale with display zoom, the text on Chrome OS
is now always rastered with the correct glyph positioning and it no
longer requires subpixel positioning.

Updates unittests.

Bug: 835187,824154,716662
Change-Id: Ibcf6314321777da81335769927d65d52911855df
Component: Text render, subpixel positioning, font
Reviewed-on: https://chromium-review.googlesource.com/1027005Reviewed-by: Dan Erat <derat@chromium.org>
Commit-Queue: Malay Keshav <malaykeshav@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553738}

ash/display/display_manager_unittest.cc

@@ -3376,97 +3376,8 @@ class FontTestHelper : public AshTestBase {
   DISALLOW_COPY_AND_ASSIGN(FontTestHelper);
 };
 
-bool IsTextSubpixelPositioningEnabled() {
-  gfx::FontRenderParams params =
-      gfx::GetFontRenderParams(gfx::FontRenderParamsQuery(), nullptr);
-  return params.subpixel_positioning;
-}
-
-gfx::FontRenderParams::Hinting GetFontHintingParams() {
-  gfx::FontRenderParams params =
-      gfx::GetFontRenderParams(gfx::FontRenderParamsQuery(), nullptr);
-  return params.hinting;
-}
-
 }  // namespace
 
-using DisplayManagerFontTest = testing::Test;
-
-TEST_F(DisplayManagerFontTest, TextSubpixelPositioningWithDsf100Internal) {
-  FontTestHelper helper(1.0f, FontTestHelper::INTERNAL);
-  ASSERT_DOUBLE_EQ(
-      1.0f,
-      display::Screen::GetScreen()->GetPrimaryDisplay().device_scale_factor());
-  EXPECT_FALSE(IsTextSubpixelPositioningEnabled());
-  EXPECT_NE(gfx::FontRenderParams::HINTING_NONE, GetFontHintingParams());
-}
-
-TEST_F(DisplayManagerFontTest, TextSubpixelPositioningWithDsf200Internal) {
-  FontTestHelper helper(2.0f, FontTestHelper::INTERNAL);
-  ASSERT_DOUBLE_EQ(
-      2.0f,
-      display::Screen::GetScreen()->GetPrimaryDisplay().device_scale_factor());
-  EXPECT_TRUE(IsTextSubpixelPositioningEnabled());
-  EXPECT_EQ(gfx::FontRenderParams::HINTING_NONE, GetFontHintingParams());
-
-  display::test::DisplayManagerTestApi(helper.display_manager())
-      .SetDisplayUIScale(display::Screen::GetScreen()->GetPrimaryDisplay().id(),
-                         2.0f);
-
-  ASSERT_DOUBLE_EQ(
-      1.0f,
-      display::Screen::GetScreen()->GetPrimaryDisplay().device_scale_factor());
-  EXPECT_FALSE(IsTextSubpixelPositioningEnabled());
-  EXPECT_NE(gfx::FontRenderParams::HINTING_NONE, GetFontHintingParams());
-}
-
-TEST_F(DisplayManagerFontTest, TextSubpixelPositioningWithDsf100External) {
-  FontTestHelper helper(1.0f, FontTestHelper::EXTERNAL);
-  ASSERT_DOUBLE_EQ(
-      1.0f,
-      display::Screen::GetScreen()->GetPrimaryDisplay().device_scale_factor());
-  EXPECT_FALSE(IsTextSubpixelPositioningEnabled());
-  EXPECT_NE(gfx::FontRenderParams::HINTING_NONE, GetFontHintingParams());
-}
-
-TEST_F(DisplayManagerFontTest, TextSubpixelPositioningWithDsf125External) {
-  FontTestHelper helper(1.25f, FontTestHelper::EXTERNAL);
-  ASSERT_DOUBLE_EQ(
-      1.25f,
-      display::Screen::GetScreen()->GetPrimaryDisplay().device_scale_factor());
-  EXPECT_TRUE(IsTextSubpixelPositioningEnabled());
-  EXPECT_EQ(gfx::FontRenderParams::HINTING_NONE, GetFontHintingParams());
-}
-
-TEST_F(DisplayManagerFontTest, TextSubpixelPositioningWithDsf200External) {
-  FontTestHelper helper(2.0f, FontTestHelper::EXTERNAL);
-  ASSERT_DOUBLE_EQ(
-      2.0f,
-      display::Screen::GetScreen()->GetPrimaryDisplay().device_scale_factor());
-  EXPECT_TRUE(IsTextSubpixelPositioningEnabled());
-  EXPECT_EQ(gfx::FontRenderParams::HINTING_NONE, GetFontHintingParams());
-}
-
-TEST_F(DisplayManagerFontTest,
-       TextSubpixelPositioningWithDsf125InternalWithScaling) {
-  FontTestHelper helper(1.25f, FontTestHelper::INTERNAL);
-  ASSERT_DOUBLE_EQ(
-      1.0f,
-      display::Screen::GetScreen()->GetPrimaryDisplay().device_scale_factor());
-  EXPECT_FALSE(IsTextSubpixelPositioningEnabled());
-  EXPECT_NE(gfx::FontRenderParams::HINTING_NONE, GetFontHintingParams());
-
-  display::test::DisplayManagerTestApi(helper.display_manager())
-      .SetDisplayUIScale(display::Screen::GetScreen()->GetPrimaryDisplay().id(),
-                         0.8f);
-
-  ASSERT_DOUBLE_EQ(
-      1.25f,
-      display::Screen::GetScreen()->GetPrimaryDisplay().device_scale_factor());
-  EXPECT_TRUE(IsTextSubpixelPositioningEnabled());
-  EXPECT_EQ(gfx::FontRenderParams::HINTING_NONE, GetFontHintingParams());
-}
-
 TEST_F(DisplayManagerTest, CheckInitializationOfRotationProperty) {
   int64_t id = display_manager()->GetDisplayAt(0).id();
   display_manager()->RegisterDisplayProperty(

ui/gfx/font_render_params_linux.cc

@@ -279,7 +279,11 @@ FontRenderParams GetFontRenderParams(const FontRenderParamsQuery& query,
     params.subpixel_rendering = FontRenderParams::SUBPIXEL_RENDERING_NONE;
     params.subpixel_positioning = false;
   } else {
+#if !defined(OS_CHROMEOS)
     params.subpixel_positioning = actual_query.device_scale_factor > 1.0f;
+#else
+    params.subpixel_positioning = false;
+#endif  // !defined(OS_CHROMEOS)
 
     // To enable subpixel positioning, we need to disable hinting.
     if (params.subpixel_positioning)

ui/gfx/font_render_params_linux_unittest.cc

@@ -310,7 +310,11 @@ TEST_F(FontRenderParamsTest, ForceSubpixelPositioning) {
     FontRenderParams params =
         GetFontRenderParams(FontRenderParamsQuery(), NULL);
     EXPECT_TRUE(params.antialiasing);
+#if !defined(OS_CHROMEOS)
     EXPECT_TRUE(params.subpixel_positioning);
+#else
+    EXPECT_FALSE(params.subpixel_positioning);
+#endif  // !defined(OS_CHROMEOS)
     SetFontRenderParamsDeviceScaleFactor(1.0f);
   }
 }