Implement prefers-contrast media query

This change adds support for the prefers-contrast media query and adds
PreferredContrast to settings. The logic for updating PreferredContrast
from its default state based on the OS will be implemented in a
follow-up change.

Spec:
https://drafts.csswg.org/mediaqueries-5/#prefers-contrast

Intent to prototype:
https://groups.google.com/a/chromium.org/g/blink-dev/c/I0e2_nAwW7E

Bug: 1107431
Change-Id: Ie09df9069c979caf944d8af1d5f6bde80f40e8ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410646
Commit-Queue: Alison Maher <almaher@microsoft.com>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818576}

third_party/blink/public/mojom/BUILD.gn

@@ -42,6 +42,7 @@ mojom("mojom_platform") {
     "crash/crash_memory_metrics_reporter.mojom",
     "credentialmanager/credential_manager.mojom",
     "css/preferred_color_scheme.mojom",
+    "css/preferred_contrast.mojom",
     "devtools/console_message.mojom",
     "devtools/devtools_agent.mojom",
     "devtools/devtools_frontend.mojom",

third_party/blink/public/mojom/css/preferred_contrast.mojom

+// Copyright 2020 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.
+
+module blink.mojom;
+
+// Spec: https://drafts.csswg.org/mediaqueries-5/#prefers-contrast
+enum PreferredContrast {
+  kMore,
+  kLess,
+  kNoPreference,
+};
\ No newline at end of file

third_party/blink/public/web/web_settings.h

@@ -35,6 +35,7 @@
 
 #include "third_party/blink/public/common/css/navigation_controls.h"
 #include "third_party/blink/public/common/web_preferences/web_preferences.h"
+#include "third_party/blink/public/mojom/css/preferred_contrast.mojom-forward.h"
 #include "third_party/blink/public/mojom/v8_cache_options.mojom-forward.h"
 #include "third_party/blink/public/mojom/webpreferences/web_preferences.mojom-forward.h"
 #include "third_party/blink/public/platform/web_common.h"
@@ -275,6 +276,7 @@ class WebSettings {
   virtual void SetLazyImageFirstKFullyLoad4G(int) = 0;
   virtual void SetForceDarkModeEnabled(bool) = 0;
   virtual void SetPreferredColorScheme(blink::mojom::PreferredColorScheme) = 0;
+  virtual void SetPreferredContrast(mojom::PreferredContrast) = 0;
   virtual void SetNavigationControls(NavigationControls) = 0;
   virtual void SetAriaModalPrunesAXTree(bool) = 0;
   virtual void SetUseAXMenuList(bool) = 0;

third_party/blink/renderer/core/css/css.dict

@@ -925,6 +925,9 @@
 "jis-b5"
 "jis-b4"
 "hidden-matchable"
+"more"
+"less"
+"forced"
 
 # at-rules
 "@charset"

third_party/blink/renderer/core/css/css_value_keywords.json5

@@ -1441,5 +1441,11 @@
     // always
     // both
     "force",
+
+    // (prefers-contrast:) media feature
+    // no-preference
+    "more",
+    "less",
+    "forced",
   ],
 }

third_party/blink/renderer/core/css/media_feature_names.json5

@@ -53,6 +53,7 @@
     "origin-trial-test",
     "pointer",
     "prefers-color-scheme",
+    "prefers-contrast",
     "prefers-reduced-motion",
     "prefers-reduced-data",
     "resolution",

third_party/blink/renderer/core/css/media_query_evaluator.cc

@@ -32,7 +32,6 @@
 #include "third_party/blink/public/common/css/forced_colors.h"
 #include "third_party/blink/public/common/css/navigation_controls.h"
 #include "third_party/blink/public/common/css/screen_spanning.h"
-#include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-blink-forward.h"
 #include "third_party/blink/public/mojom/manifest/display_mode.mojom-shared.h"
 #include "third_party/blink/renderer/core/css/css_primitive_value.h"
 #include "third_party/blink/renderer/core/css/css_resolution_units.h"
@@ -865,6 +864,37 @@ static bool PrefersColorSchemeMediaFeatureEval(
           value.id == CSSValueID::kLight);
 }
 
+static bool PrefersContrastMediaFeatureEval(const MediaQueryExpValue& value,
+                                            MediaFeaturePrefix,
+                                            const MediaValues& media_values) {
+  auto preferred_contrast = media_values.GetPreferredContrast();
+  ForcedColors forced_colors = media_values.GetForcedColors();
+
+  if (!value.IsValid()) {
+    return forced_colors != ForcedColors::kNone ||
+           preferred_contrast != mojom::blink::PreferredContrast::kNoPreference;
+  }
+
+  if (!value.is_id)
+    return false;
+
+  switch (value.id) {
+    case CSSValueID::kForced:
+      return forced_colors == ForcedColors::kActive;
+    case CSSValueID::kMore:
+      return preferred_contrast == mojom::blink::PreferredContrast::kMore;
+    case CSSValueID::kLess:
+      return preferred_contrast == mojom::blink::PreferredContrast::kLess;
+    case CSSValueID::kNoPreference:
+      return forced_colors != ForcedColors::kActive &&
+             preferred_contrast ==
+                 mojom::blink::PreferredContrast::kNoPreference;
+    default:
+      NOTREACHED();
+      return false;
+  }
+}
+
 static bool ForcedColorsMediaFeatureEval(const MediaQueryExpValue& value,
                                          MediaFeaturePrefix,
                                          const MediaValues& media_values) {

third_party/blink/renderer/core/css/media_query_evaluator_test.cc

@@ -187,6 +187,60 @@ MediaQueryEvaluatorTestCase g_forcedcolors_none_cases[] = {
     {nullptr, 0}  // Do not remove the terminator line.
 };
 
+MediaQueryEvaluatorTestCase g_preferscontrast_nopreference_cases[] = {
+    {"(prefers-contrast)", 0},
+    {"(prefers-contrast: more)", 0},
+    {"(prefers-contrast: less)", 0},
+    {"(prefers-contrast: forced)", 0},
+    {"(prefers-contrast: no-preference)", 1},
+    {nullptr, 0}  // Do not remove the terminator line.
+};
+
+MediaQueryEvaluatorTestCase g_preferscontrast_more_cases[] = {
+    {"(prefers-contrast)", 1},
+    {"(prefers-contrast: more)", 1},
+    {"(prefers-contrast: less)", 0},
+    {"(prefers-contrast: forced)", 0},
+    {"(prefers-contrast: no-preference)", 0},
+    {nullptr, 0}  // Do not remove the terminator line.
+};
+
+MediaQueryEvaluatorTestCase g_preferscontrast_less_cases[] = {
+    {"(prefers-contrast)", 1},
+    {"(prefers-contrast: more)", 0},
+    {"(prefers-contrast: less)", 1},
+    {"(prefers-contrast: forced)", 0},
+    {"(prefers-contrast: no-preference)", 0},
+    {nullptr, 0}  // Do not remove the terminator line.
+};
+
+MediaQueryEvaluatorTestCase g_preferscontrast_forced_cases[] = {
+    {"(prefers-contrast)", 1},
+    {"(prefers-contrast: more)", 0},
+    {"(prefers-contrast: less)", 0},
+    {"(prefers-contrast: forced)", 1},
+    {"(prefers-contrast: no-preference)", 0},
+    {nullptr, 0}  // Do not remove the terminator line.
+};
+
+MediaQueryEvaluatorTestCase g_preferscontrast_forced_more_cases[] = {
+    {"(prefers-contrast)", 1},
+    {"(prefers-contrast: more)", 1},
+    {"(prefers-contrast: less)", 0},
+    {"(prefers-contrast: forced)", 1},
+    {"(prefers-contrast: no-preference)", 0},
+    {nullptr, 0}  // Do not remove the terminator line.
+};
+
+MediaQueryEvaluatorTestCase g_preferscontrast_forced_less_cases[] = {
+    {"(prefers-contrast)", 1},
+    {"(prefers-contrast: more)", 0},
+    {"(prefers-contrast: less)", 1},
+    {"(prefers-contrast: forced)", 1},
+    {"(prefers-contrast: no-preference)", 0},
+    {nullptr, 0}  // Do not remove the terminator line.
+};
+
 MediaQueryEvaluatorTestCase g_navigationcontrols_back_button_cases[] = {
     {"(navigation-controls: back-button)", 1},
     {"(navigation-controls: none)", 0},
@@ -398,6 +452,61 @@ TEST(MediaQueryEvaluatorTest, CachedForcedColors) {
   }
 }
 
+TEST(MediaQueryEvaluatorTest, CachedPrefersContrast) {
+  ScopedForcedColorsForTest forced_scoped_feature(true);
+  ScopedPrefersContrastForTest contrast_scoped_feature(true);
+
+  MediaValuesCached::MediaValuesCachedData data;
+  data.forced_colors = ForcedColors::kNone;
+  data.preferred_contrast = mojom::blink::PreferredContrast::kNoPreference;
+  MediaValues* media_values = MakeGarbageCollected<MediaValuesCached>(data);
+
+  // Prefers-contrast - no-preference.
+  MediaQueryEvaluator media_query_evaluator(*media_values);
+  TestMQEvaluator(g_preferscontrast_nopreference_cases, media_query_evaluator);
+
+  // Prefers-contrast - more.
+  {
+    data.preferred_contrast = mojom::blink::PreferredContrast::kMore;
+    MediaValues* media_values = MakeGarbageCollected<MediaValuesCached>(data);
+    MediaQueryEvaluator media_query_evaluator(*media_values);
+    TestMQEvaluator(g_preferscontrast_more_cases, media_query_evaluator);
+  }
+
+  // Prefers-contrast - less.
+  {
+    data.preferred_contrast = mojom::blink::PreferredContrast::kLess;
+    MediaValues* media_values = MakeGarbageCollected<MediaValuesCached>(data);
+    MediaQueryEvaluator media_query_evaluator(*media_values);
+    TestMQEvaluator(g_preferscontrast_less_cases, media_query_evaluator);
+  }
+
+  // Prefers-contrast - forced.
+  {
+    data.preferred_contrast = mojom::blink::PreferredContrast::kNoPreference;
+    data.forced_colors = ForcedColors::kActive;
+    MediaValues* media_values = MakeGarbageCollected<MediaValuesCached>(data);
+    MediaQueryEvaluator media_query_evaluator(*media_values);
+    TestMQEvaluator(g_preferscontrast_forced_cases, media_query_evaluator);
+  }
+
+  // Prefers-contrast - forced and more.
+  {
+    data.preferred_contrast = mojom::blink::PreferredContrast::kMore;
+    MediaValues* media_values = MakeGarbageCollected<MediaValuesCached>(data);
+    MediaQueryEvaluator media_query_evaluator(*media_values);
+    TestMQEvaluator(g_preferscontrast_forced_more_cases, media_query_evaluator);
+  }
+
+  // Prefers-contrast - forced and less.
+  {
+    data.preferred_contrast = mojom::blink::PreferredContrast::kLess;
+    MediaValues* media_values = MakeGarbageCollected<MediaValuesCached>(data);
+    MediaQueryEvaluator media_query_evaluator(*media_values);
+    TestMQEvaluator(g_preferscontrast_forced_less_cases, media_query_evaluator);
+  }
+}
+
 TEST(MediaQueryEvaluatorTest, CachedScreenSpanning) {
   ScopedCSSFoldablesForTest scoped_feature(true);
 

third_party/blink/renderer/core/css/media_query_exp.cc

@@ -79,6 +79,13 @@ static inline bool FeatureWithValidIdent(const String& media_feature,
   if (media_feature == media_feature_names::kPrefersColorSchemeMediaFeature)
     return ident == CSSValueID::kDark || ident == CSSValueID::kLight;
 
+  if (RuntimeEnabledFeatures::PrefersContrastEnabled()) {
+    if (media_feature == media_feature_names::kPrefersContrastMediaFeature) {
+      return ident == CSSValueID::kNoPreference || ident == CSSValueID::kMore ||
+             ident == CSSValueID::kLess || ident == CSSValueID::kForced;
+    }
+  }
+
   if (media_feature == media_feature_names::kPrefersReducedMotionMediaFeature)
     return ident == CSSValueID::kNoPreference || ident == CSSValueID::kReduce;
 
@@ -219,6 +226,8 @@ static inline bool FeatureWithoutValue(
          media_feature == media_feature_names::kImmersiveMediaFeature ||
          media_feature ==
              media_feature_names::kPrefersColorSchemeMediaFeature ||
+         (media_feature == media_feature_names::kPrefersContrastMediaFeature &&
+          RuntimeEnabledFeatures::PrefersContrastEnabled()) ||
          media_feature ==
              media_feature_names::kPrefersReducedMotionMediaFeature ||
          (media_feature ==

third_party/blink/renderer/core/css/media_values.cc

@@ -6,7 +6,6 @@
 
 #include "third_party/blink/public/common/css/screen_spanning.h"
 #include "third_party/blink/public/common/widget/screen_info.h"
-#include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-blink.h"
 #include "third_party/blink/public/platform/platform.h"
 #include "third_party/blink/public/platform/web_theme_engine.h"
 #include "third_party/blink/renderer/core/css/css_resolution_units.h"
@@ -196,6 +195,13 @@ mojom::blink::PreferredColorScheme MediaValues::CalculatePreferredColorScheme(
   return frame->GetDocument()->GetStyleEngine().GetPreferredColorScheme();
 }
 
+mojom::blink::PreferredContrast MediaValues::CalculatePreferredContrast(
+    LocalFrame* frame) {
+  DCHECK(frame);
+  DCHECK(frame->GetSettings());
+  return frame->GetSettings()->GetPreferredContrast();
+}
+
 bool MediaValues::CalculatePrefersReducedMotion(LocalFrame* frame) {
   DCHECK(frame);
   DCHECK(frame->GetSettings());

third_party/blink/renderer/core/css/media_values.h

@@ -6,6 +6,7 @@
 #define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_MEDIA_VALUES_H_
 
 #include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-blink-forward.h"
+#include "third_party/blink/public/mojom/css/preferred_contrast.mojom-blink-forward.h"
 #include "third_party/blink/public/mojom/manifest/display_mode.mojom-shared.h"
 #include "third_party/blink/renderer/core/core_export.h"
 #include "third_party/blink/renderer/core/css/css_primitive_value.h"
@@ -19,7 +20,6 @@ class CSSPrimitiveValue;
 class LocalFrame;
 enum class CSSValueID;
 enum class ColorSpaceGamut;
-enum class PreferredColorScheme;
 enum class ForcedColors;
 enum class NavigationControls;
 enum class ScreenSpanning;
@@ -85,6 +85,7 @@ class CORE_EXPORT MediaValues : public GarbageCollected<MediaValues> {
   virtual ColorSpaceGamut ColorGamut() const = 0;
   virtual mojom::blink::PreferredColorScheme GetPreferredColorScheme()
       const = 0;
+  virtual mojom::blink::PreferredContrast GetPreferredContrast() const = 0;
   virtual bool PrefersReducedMotion() const = 0;
   virtual bool PrefersReducedData() const = 0;
   virtual ForcedColors GetForcedColors() const = 0;
@@ -112,6 +113,8 @@ class CORE_EXPORT MediaValues : public GarbageCollected<MediaValues> {
   static ColorSpaceGamut CalculateColorGamut(LocalFrame*);
   static mojom::blink::PreferredColorScheme CalculatePreferredColorScheme(
       LocalFrame*);
+  static mojom::blink::PreferredContrast CalculatePreferredContrast(
+      LocalFrame*);
   static bool CalculatePrefersReducedMotion(LocalFrame*);
   static bool CalculatePrefersReducedData(LocalFrame*);
   static ForcedColors CalculateForcedColors();

third_party/blink/renderer/core/css/media_values_cached.cc

@@ -8,6 +8,7 @@
 #include "third_party/blink/public/common/css/navigation_controls.h"
 #include "third_party/blink/public/common/css/screen_spanning.h"
 #include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-blink.h"
+#include "third_party/blink/public/mojom/css/preferred_contrast.mojom-blink.h"
 #include "third_party/blink/renderer/core/css/css_primitive_value.h"
 #include "third_party/blink/renderer/core/dom/document.h"
 #include "third_party/blink/renderer/core/frame/local_frame.h"
@@ -35,6 +36,7 @@ MediaValuesCached::MediaValuesCachedData::MediaValuesCachedData()
       display_mode(blink::mojom::DisplayMode::kBrowser),
       color_gamut(ColorSpaceGamut::kUnknown),
       preferred_color_scheme(mojom::blink::PreferredColorScheme::kLight),
+      preferred_contrast(mojom::blink::PreferredContrast::kNoPreference),
       prefers_reduced_motion(false),
       forced_colors(ForcedColors::kNone),
       navigation_controls(NavigationControls::kNone),
@@ -77,6 +79,7 @@ MediaValuesCached::MediaValuesCachedData::MediaValuesCachedData(
     media_type = MediaValues::CalculateMediaType(frame);
     color_gamut = MediaValues::CalculateColorGamut(frame);
     preferred_color_scheme = MediaValues::CalculatePreferredColorScheme(frame);
+    preferred_contrast = MediaValues::CalculatePreferredContrast(frame);
     prefers_reduced_motion = MediaValues::CalculatePrefersReducedMotion(frame);
     prefers_reduced_data = MediaValues::CalculatePrefersReducedData(frame);
     forced_colors = MediaValues::CalculateForcedColors();
@@ -197,6 +200,11 @@ mojom::blink::PreferredColorScheme MediaValuesCached::GetPreferredColorScheme()
   return data_.preferred_color_scheme;
 }
 
+mojom::blink::PreferredContrast MediaValuesCached::GetPreferredContrast()
+    const {
+  return data_.preferred_contrast;
+}
+
 bool MediaValuesCached::PrefersReducedMotion() const {
   return data_.prefers_reduced_motion;
 }

third_party/blink/renderer/core/css/media_values_cached.h

@@ -5,7 +5,6 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_CSS_MEDIA_VALUES_CACHED_H_
 #define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_MEDIA_VALUES_CACHED_H_
 
-#include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-blink-forward.h"
 #include "third_party/blink/renderer/core/core_export.h"
 #include "third_party/blink/renderer/core/css/media_values.h"
 #include "third_party/blink/renderer/platform/wtf/cross_thread_copier.h"
@@ -37,6 +36,7 @@ class CORE_EXPORT MediaValuesCached final : public MediaValues {
     blink::mojom::DisplayMode display_mode;
     ColorSpaceGamut color_gamut;
     mojom::blink::PreferredColorScheme preferred_color_scheme;
+    mojom::blink::PreferredContrast preferred_contrast;
     bool prefers_reduced_motion;
     bool prefers_reduced_data = false;
     ForcedColors forced_colors;
@@ -67,6 +67,7 @@ class CORE_EXPORT MediaValuesCached final : public MediaValues {
       data.display_mode = display_mode;
       data.color_gamut = color_gamut;
       data.preferred_color_scheme = preferred_color_scheme;
+      data.preferred_contrast = preferred_contrast;
       data.prefers_reduced_motion = prefers_reduced_motion;
       data.prefers_reduced_data = prefers_reduced_data;
       data.forced_colors = forced_colors;
@@ -108,6 +109,7 @@ class CORE_EXPORT MediaValuesCached final : public MediaValues {
   blink::mojom::DisplayMode DisplayMode() const override;
   ColorSpaceGamut ColorGamut() const override;
   mojom::blink::PreferredColorScheme GetPreferredColorScheme() const override;
+  mojom::blink::PreferredContrast GetPreferredContrast() const override;
   bool PrefersReducedMotion() const override;
   bool PrefersReducedData() const override;
   ForcedColors GetForcedColors() const override;

third_party/blink/renderer/core/css/media_values_dynamic.cc

@@ -6,7 +6,6 @@
 
 #include "third_party/blink/public/common/css/forced_colors.h"
 #include "third_party/blink/public/common/css/navigation_controls.h"
-#include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-blink-forward.h"
 #include "third_party/blink/renderer/core/css/css_primitive_value.h"
 #include "third_party/blink/renderer/core/css/css_resolution_units.h"
 #include "third_party/blink/renderer/core/css/css_to_length_conversion_data.h"
@@ -145,6 +144,11 @@ mojom::blink::PreferredColorScheme MediaValuesDynamic::GetPreferredColorScheme()
   return CalculatePreferredColorScheme(frame_);
 }
 
+mojom::blink::PreferredContrast MediaValuesDynamic::GetPreferredContrast()
+    const {
+  return CalculatePreferredContrast(frame_);
+}
+
 bool MediaValuesDynamic::PrefersReducedMotion() const {
   return CalculatePrefersReducedMotion(frame_);
 }

third_party/blink/renderer/core/css/media_values_dynamic.h

@@ -48,6 +48,7 @@ class CORE_EXPORT MediaValuesDynamic : public MediaValues {
   blink::mojom::DisplayMode DisplayMode() const override;
   ColorSpaceGamut ColorGamut() const override;
   mojom::blink::PreferredColorScheme GetPreferredColorScheme() const override;
+  mojom::blink::PreferredContrast GetPreferredContrast() const override;
   bool PrefersReducedMotion() const override;
   bool PrefersReducedData() const override;
   ForcedColors GetForcedColors() const override;

third_party/blink/renderer/core/css/style_engine_test.cc

@@ -9,7 +9,6 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/blink/public/common/css/forced_colors.h"
 #include "third_party/blink/public/common/css/navigation_controls.h"
-#include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-blink-forward.h"
 #include "third_party/blink/public/platform/web_theme_engine.h"
 #include "third_party/blink/renderer/bindings/core/v8/v8_binding_for_core.h"
 #include "third_party/blink/renderer/bindings/core/v8/v8_shadow_root_init.h"
@@ -1544,6 +1543,125 @@ TEST_F(StyleEngineTest, MediaQueriesChangeColorSchemeForcedDarkMode) {
                 GetCSSPropertyColor()));
 }
 
+TEST_F(StyleEngineTest, MediaQueriesChangePrefersContrast) {
+  ScopedForcedColorsForTest forced_scoped_feature(true);
+  ScopedPrefersContrastForTest contrast_scoped_feature(true);
+
+  ColorSchemeHelper color_scheme_helper(GetDocument());
+  color_scheme_helper.SetPreferredContrast(
+      mojom::blink::PreferredContrast::kNoPreference);
+  color_scheme_helper.SetForcedColors(GetDocument(), ForcedColors::kNone);
+
+  GetDocument().body()->setInnerHTML(R"HTML(
+    <style>
+      body { color: red; forced-color-adjust: none; }
+      @media (prefers-contrast: no-preference) {
+        body { color: green }
+      }
+      @media (prefers-contrast) {
+        body { color: blue }
+      }
+    </style>
+    <body></body>
+  )HTML");
+
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(0, 128, 0),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+
+  color_scheme_helper.SetPreferredContrast(
+      mojom::blink::PreferredContrast::kMore);
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(0, 0, 255),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+
+  color_scheme_helper.SetPreferredContrast(
+      mojom::blink::PreferredContrast::kLess);
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(0, 0, 255),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+
+  color_scheme_helper.SetForcedColors(GetDocument(), ForcedColors::kActive);
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(0, 0, 255),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+}
+
+TEST_F(StyleEngineTest, MediaQueriesChangeSpecificPrefersContrast) {
+  ScopedForcedColorsForTest forced_scoped_feature(true);
+  ScopedPrefersContrastForTest contrast_scoped_feature(true);
+
+  ColorSchemeHelper color_scheme_helper(GetDocument());
+  color_scheme_helper.SetPreferredContrast(
+      mojom::blink::PreferredContrast::kNoPreference);
+  color_scheme_helper.SetForcedColors(GetDocument(), ForcedColors::kNone);
+
+  GetDocument().body()->setInnerHTML(R"HTML(
+    <style>
+      body { color: red; forced-color-adjust: none; }
+      @media (prefers-contrast: more) {
+        body { color: blue }
+      }
+      @media (prefers-contrast: less) {
+        body { color: orange }
+      }
+      @media (prefers-contrast: forced) {
+        body { color: yellow }
+      }
+      @media (prefers-contrast: forced) and (prefers-contrast: more) {
+        body { color: green }
+      }
+      @media (prefers-contrast: forced) and (prefers-contrast: less) {
+        body { color: purple }
+      }
+    </style>
+    <body></body>
+  )HTML");
+
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(255, 0, 0),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+
+  color_scheme_helper.SetPreferredContrast(
+      mojom::blink::PreferredContrast::kMore);
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(0, 0, 255),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+
+  color_scheme_helper.SetPreferredContrast(
+      mojom::blink::PreferredContrast::kLess);
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(255, 165, 0),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+
+  color_scheme_helper.SetForcedColors(GetDocument(), ForcedColors::kActive);
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(128, 0, 128),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+
+  color_scheme_helper.SetPreferredContrast(
+      mojom::blink::PreferredContrast::kMore);
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(0, 128, 0),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+
+  color_scheme_helper.SetPreferredContrast(
+      mojom::blink::PreferredContrast::kNoPreference);
+  UpdateAllLifecyclePhases();
+  EXPECT_EQ(MakeRGB(255, 255, 0),
+            GetDocument().body()->GetComputedStyle()->VisitedDependentColor(
+                GetCSSPropertyColor()));
+}
+
 TEST_F(StyleEngineTest, MediaQueriesChangePrefersReducedMotion) {
   GetDocument().body()->setInnerHTML(R"HTML(
     <style>

third_party/blink/renderer/core/exported/web_settings_impl.cc

@@ -775,6 +775,11 @@ void WebSettingsImpl::SetPreferredColorScheme(
   settings_->SetPreferredColorScheme(color_scheme);
 }
 
+void WebSettingsImpl::SetPreferredContrast(
+    mojom::blink::PreferredContrast contrast) {
+  settings_->SetPreferredContrast(contrast);
+}
+
 void WebSettingsImpl::SetNavigationControls(
     NavigationControls navigation_controls) {
   settings_->SetNavigationControls(navigation_controls);

third_party/blink/renderer/core/exported/web_settings_impl.h

@@ -31,6 +31,7 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_EXPORTED_WEB_SETTINGS_IMPL_H_
 #define THIRD_PARTY_BLINK_RENDERER_CORE_EXPORTED_WEB_SETTINGS_IMPL_H_
 
+#include "third_party/blink/public/mojom/css/preferred_contrast.mojom-blink.h"
 #include "third_party/blink/public/mojom/v8_cache_options.mojom-blink.h"
 #include "third_party/blink/public/mojom/webpreferences/web_preferences.mojom-blink.h"
 #include "third_party/blink/public/web/web_settings.h"
@@ -223,6 +224,7 @@ class CORE_EXPORT WebSettingsImpl final : public WebSettings {
 
   void SetForceDarkModeEnabled(bool) override;
   void SetPreferredColorScheme(mojom::blink::PreferredColorScheme) override;
+  void SetPreferredContrast(mojom::blink::PreferredContrast) override;
   void SetNavigationControls(NavigationControls) override;
 
   void SetAriaModalPrunesAXTree(bool) override;

third_party/blink/renderer/core/frame/settings.h

@@ -32,7 +32,7 @@
 
 #include "base/macros.h"
 #include "third_party/blink/public/common/css/navigation_controls.h"
-#include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-blink-forward.h"
+#include "third_party/blink/public/mojom/css/preferred_contrast.mojom-blink.h"
 #include "third_party/blink/public/mojom/manifest/display_mode.mojom-shared.h"
 #include "third_party/blink/public/mojom/v8_cache_options.mojom-blink.h"
 #include "third_party/blink/public/mojom/webpreferences/web_preferences.mojom-blink.h"

third_party/blink/renderer/core/frame/settings.json5

@@ -1011,6 +1011,15 @@
       type: "mojom::blink::PreferredColorScheme",
     },
 
+    // Preferred contrast from the OS/application passed to the renderer for
+    // evaluating the prefers-contrast media query.
+    {
+      name: "preferredContrast",
+      initial: "mojom::blink::PreferredContrast::kNoPreference",
+      invalidate: "MediaQuery",
+      type: "mojom::blink::PreferredContrast",
+    },
+
     // Preferred motion-reduction setting from the OS/application passed to the
     // renderer for evaluating the prefers-reduced-motion media query.
     {

third_party/blink/renderer/core/testing/color_scheme_helper.cc

@@ -4,7 +4,6 @@
 
 #include "third_party/blink/renderer/core/testing/color_scheme_helper.h"
 
-#include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-blink.h"
 #include "third_party/blink/public/platform/platform.h"
 #include "third_party/blink/public/platform/web_theme_engine.h"
 #include "third_party/blink/renderer/core/dom/document.h"
@@ -18,6 +17,7 @@ ColorSchemeHelper::ColorSchemeHelper(Document& document)
   DCHECK(Platform::Current() && Platform::Current()->ThemeEngine());
   web_theme_engine_ = Platform::Current()->ThemeEngine();
   default_preferred_color_scheme_ = settings_.GetPreferredColorScheme();
+  default_preferred_contrast_ = settings_.GetPreferredContrast();
   default_forced_colors_ = web_theme_engine_->GetForcedColors();
 }
 
@@ -26,12 +26,15 @@ ColorSchemeHelper::ColorSchemeHelper(Page& page)
   DCHECK(Platform::Current() && Platform::Current()->ThemeEngine());
   web_theme_engine_ = Platform::Current()->ThemeEngine();
   default_preferred_color_scheme_ = settings_.GetPreferredColorScheme();
+  default_preferred_contrast_ = settings_.GetPreferredContrast();
   default_forced_colors_ = web_theme_engine_->GetForcedColors();
 }
 
 ColorSchemeHelper::~ColorSchemeHelper() {
-  // Reset preferred color scheme and forced colors to their original values.
+  // Reset preferred color scheme, preferred contrast and forced colors to their
+  // original values.
   settings_.SetPreferredColorScheme(default_preferred_color_scheme_);
+  settings_.SetPreferredContrast(default_preferred_contrast_);
   web_theme_engine_->SetForcedColors(default_forced_colors_);
 }
 
@@ -40,6 +43,11 @@ void ColorSchemeHelper::SetPreferredColorScheme(
   settings_.SetPreferredColorScheme(preferred_color_scheme);
 }
 
+void ColorSchemeHelper::SetPreferredContrast(
+    const mojom::blink::PreferredContrast preferred_contrast) {
+  settings_.SetPreferredContrast(preferred_contrast);
+}
+
 void ColorSchemeHelper::SetForcedColors(Document& document,
                                         const ForcedColors forced_colors) {
   web_theme_engine_->SetForcedColors(forced_colors);

third_party/blink/renderer/core/testing/color_scheme_helper.h

@@ -7,6 +7,7 @@
 
 #include "third_party/blink/public/common/css/forced_colors.h"
 #include "third_party/blink/public/mojom/css/preferred_color_scheme.mojom-shared.h"
+#include "third_party/blink/public/mojom/css/preferred_contrast.mojom-shared.h"
 
 namespace blink {
 
@@ -15,9 +16,10 @@ class Page;
 class Settings;
 class WebThemeEngine;
 
-// ColorSchemeHelper is used to update the values of PreferredColorScheme and
-// ForcedColors for testing. ColorSchemeHelper will reset PreferredColorScheme
-// and ForcedColors back to their default values upon deconstruction.
+// ColorSchemeHelper is used to update the values of PreferredColorScheme,
+// PreferredContrast and ForcedColors for testing. ColorSchemeHelper will reset
+// PreferredColorScheme, PreferredContrast and ForcedColors back to their
+// default values upon deconstruction.
 class ColorSchemeHelper {
  public:
   ColorSchemeHelper(Document& document);
@@ -26,6 +28,7 @@ class ColorSchemeHelper {
 
   void SetPreferredColorScheme(
       const mojom::PreferredColorScheme preferred_color_scheme);
+  void SetPreferredContrast(const mojom::PreferredContrast preferred_contrast);
   void SetForcedColors(Document& document, const ForcedColors forced_colors);
   void SetForcedColors(Page& page, const ForcedColors forced_colors);
 
@@ -34,6 +37,8 @@ class ColorSchemeHelper {
   Settings& settings_;
   mojom::PreferredColorScheme default_preferred_color_scheme_ =
       mojom::PreferredColorScheme::kLight;
+  mojom::PreferredContrast default_preferred_contrast_ =
+      mojom::PreferredContrast::kNoPreference;
   ForcedColors default_forced_colors_ = ForcedColors::kNone;
 };
 

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1535,6 +1535,10 @@
       name: "PreferNonCompositedScrolling",
       settable_from_internals: true,
     },
+    {
+      name: "PrefersContrast",
+      depends_on: ["ForcedColors"],
+    },
     {
       name: 'PrefersReducedData',
       status: 'experimental',