mac: add high contrast theme

This change adds a high-contrast theme supplier (IncreasedContrastThemeSupplier)
and enables it on Mac when the system "Increase Contrast" setting is enabled,
or when --force-high-contrast is passed at startup. This theme maximizes
contrast between UI elements.

Bug: 831769
Change-Id: I6cbb1b67fd95372dd65501feab6639942f767019
Reviewed-on: https://chromium-review.googlesource.com/1142030Reviewed-by: Evan Stade <estade@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576467}

chrome/browser/BUILD.gn

@@ -2936,6 +2936,8 @@ jumbo_split_static_library("browser") {
       "themes/browser_theme_pack.h",
       "themes/custom_theme_supplier.cc",
       "themes/custom_theme_supplier.h",
+      "themes/increased_contrast_theme_supplier.cc",
+      "themes/increased_contrast_theme_supplier.h",
       "themes/theme_properties.cc",
       "themes/theme_service.cc",
       "themes/theme_service.h",

chrome/browser/themes/custom_theme_supplier.h

@@ -34,6 +34,7 @@ class CustomThemeSupplier
     EXTENSION,
     NATIVE_X11,
     SUPERVISED_USER_THEME,
+    INCREASED_CONTRAST,
   };
 
   explicit CustomThemeSupplier(ThemeType type);

chrome/browser/themes/increased_contrast_theme_supplier.cc

+// Copyright 2018 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 "chrome/browser/themes/increased_contrast_theme_supplier.h"
+#include "chrome/browser/themes/theme_properties.h"
+
+IncreasedContrastThemeSupplier::IncreasedContrastThemeSupplier()
+    : CustomThemeSupplier(INCREASED_CONTRAST) {}
+IncreasedContrastThemeSupplier::~IncreasedContrastThemeSupplier() {}
+
+// TODO(ellyjones): Follow up with a11y designers about these color choices.
+bool IncreasedContrastThemeSupplier::GetColor(int id, SkColor* color) const {
+  switch (id) {
+    case ThemeProperties::COLOR_TAB_TEXT:
+      *color = SK_ColorBLACK;
+      return true;
+    case ThemeProperties::COLOR_BACKGROUND_TAB_TEXT:
+      *color = SK_ColorWHITE;
+      return true;
+    case ThemeProperties::COLOR_TOOLBAR:
+      *color = SK_ColorWHITE;
+      return true;
+    case ThemeProperties::COLOR_FRAME_INACTIVE:
+      *color = SK_ColorGRAY;
+      return true;
+    case ThemeProperties::COLOR_FRAME:
+      *color = SK_ColorDKGRAY;
+      return true;
+    case ThemeProperties::COLOR_FRAME_INCOGNITO:
+      *color = SK_ColorDKGRAY;
+      return true;
+    case ThemeProperties::COLOR_TOOLBAR_TOP_SEPARATOR:
+      *color = SK_ColorLTGRAY;
+      return true;
+    case ThemeProperties::COLOR_TOOLBAR_BOTTOM_SEPARATOR:
+      *color = SK_ColorBLACK;
+      return true;
+    case ThemeProperties::COLOR_LOCATION_BAR_BORDER:
+      *color = SK_ColorBLACK;
+      return true;
+  }
+  return false;
+}

chrome/browser/themes/increased_contrast_theme_supplier.h

+// Copyright 2018 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.
+
+#ifndef CHROME_BROWSER_THEMES_INCREASED_CONTRAST_THEME_SUPPLIER_H_
+#define CHROME_BROWSER_THEMES_INCREASED_CONTRAST_THEME_SUPPLIER_H_
+
+#include "chrome/browser/themes/custom_theme_supplier.h"
+
+// A theme supplier that maximizes the contrast between UI elements and
+// especially the visual prominence of key UI elements (omnibox, active vs
+// inactive tab distinction).
+class IncreasedContrastThemeSupplier : public CustomThemeSupplier {
+ public:
+  IncreasedContrastThemeSupplier();
+
+  bool GetColor(int id, SkColor* color) const override;
+
+ protected:
+  ~IncreasedContrastThemeSupplier() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(IncreasedContrastThemeSupplier);
+};
+
+#endif  // CHROME_BROWSER_THEMES_INCREASED_CONTRAST_THEME_SUPPLIER_H_

chrome/browser/themes/theme_service.cc

@@ -27,6 +27,7 @@
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/themes/browser_theme_pack.h"
 #include "chrome/browser/themes/custom_theme_supplier.h"
+#include "chrome/browser/themes/increased_contrast_theme_supplier.h"
 #include "chrome/browser/themes/theme_properties.h"
 #include "chrome/browser/themes/theme_service_factory.h"
 #include "chrome/browser/themes/theme_syncable_service.h"
@@ -314,6 +315,11 @@ void ThemeService::UseDefaultTheme() {
     SetSupervisedUserTheme();
     return;
   }
+#endif
+#if defined(OS_MACOSX)
+  // TODO(ellyjones): Expand ShouldIncreaseContrast() to non-Mac platforms.
+  if (original_theme_provider_.ShouldIncreaseContrast())
+    SetCustomDefaultTheme(new IncreasedContrastThemeSupplier);
 #endif
   ClearAllThemeData();
   NotifyThemeChanged();

chrome/browser/ui/views/location_bar/location_bar_view.cc

@@ -118,9 +118,15 @@ namespace {
 
 // Helper function to create a rounded rect background (no stroke).
 std::unique_ptr<views::Background> CreateRoundRectBackground(SkColor bg_color,
-                                                             float radius) {
-  std::unique_ptr<views::Background> background = CreateBackgroundFromPainter(
-      views::Painter::CreateSolidRoundRectPainter(bg_color, radius));
+                                                             float radius,
+                                                             SkColor fg_color) {
+  auto painter =
+      fg_color != SK_ColorTRANSPARENT
+          ? views::Painter::CreateRoundRectWith1PxBorderPainter(
+                bg_color, fg_color, radius)
+          : views::Painter::CreateSolidRoundRectPainter(bg_color, radius);
+  std::unique_ptr<views::Background> background =
+      CreateBackgroundFromPainter(std::move(painter));
   background->SetNativeControlColor(bg_color);
   return background;
 }
@@ -789,8 +795,12 @@ void LocationBarView::RefreshBackground() {
   if (is_popup_mode_) {
     SetBackground(views::CreateSolidBackground(background_color));
   } else if (IsRounded()) {
-    SetBackground(
-        CreateRoundRectBackground(background_color, GetBorderRadius()));
+    // High contrast schemes get a border stroke even on a rounded omnibox.
+    SkColor fg_color = GetNativeTheme()->UsesHighContrastColors()
+                           ? border_color
+                           : SK_ColorTRANSPARENT;
+    SetBackground(CreateRoundRectBackground(background_color, GetBorderRadius(),
+                                            fg_color));
   } else {
     SetBackground(std::make_unique<BackgroundWith1PxBorder>(background_color,
                                                             border_color));