Specify color for focus ring

Fix brave/brave-browser#1190

In Chromium, this is specified in Native Theme, and overriden on macOS from the OS-level focus border color, but only for light theme (i.e. not incognito). In lieu of overriding all the Native Themes, this provides the 1 specific color to the FocusRing view. Whilst we may very well subclass all the Native Themes at some point, this is a pain-free way to get there for this feature of the design spec now.

browser/ui/views/frame/brave_browser_frame.cc

@@ -18,6 +18,10 @@ BraveBrowserFrame::~BraveBrowserFrame() {
 }
 
 const ui::NativeTheme* BraveBrowserFrame::GetNativeTheme() const {
+  // Gets the platform-specific override for NativeTheme,
+  // unless we're in dark mode in which case get cross-platform
+  // dark theme.
+  // TODO: Have platform-specific version of dark theme too.
 #if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_CHROMEOS)
   BraveThemeType active_builtin_theme =
             BraveThemeService::GetActiveBraveThemeType(
@@ -28,5 +32,7 @@ const ui::NativeTheme* BraveBrowserFrame::GetNativeTheme() const {
     return ui::NativeThemeDarkAura::instance();
   }
 #endif
+  // Each platform will implement ui::NativeTheme::GetInstanceForNativeUi
+  // separately, which Widget::GetNativeTheme calls.
   return views::Widget::GetNativeTheme();
 }

chromium_src/ui/views/controls/focus_ring.cc

@@ -0,0 +1,49 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "base/no_destructor.h"
+#include "ui/gfx/skia_util.h"
+#include "ui/gfx/color_palette.h"
+
+// include header first so that GetNativeTheme redefine doesn't flow to View
+#include "ui/views/controls/focus_ring.h"
+
+// Override the Focus Ring's color.
+// In Chromium, this is specified via platform-specfic native theme,
+// using kColorId_FocusedBorderColor. However, only macOS Light native theme
+// overrides this. Since we do not have a Brave version of either
+// platform-specific, or common versions, and we only want to override a single
+// color, we use this micro-theme for the FocusRingView.
+namespace {
+
+class FocusRingTheme {
+  public:
+    SkColor GetSystemColor(int id) {
+      // At the time of implementation, only two Color IDs were possible.
+      // If this changes, consider overriding NativeTheme, or moving to
+      // ThemeProperties.
+      DCHECK(id == ui::NativeTheme::kColorId_FocusedBorderColor ||
+              id == ui::NativeTheme::kColorId_AlertSeverityHigh);
+      // Must be colors that are OK on dark or light bg since this is
+      // a very simplistic implementation.
+      switch (id) {
+        case ui::NativeTheme::kColorId_FocusedBorderColor:
+          return SkColorSetRGB(0xfb, 0x54, 0x2b);
+        case ui::NativeTheme::kColorId_AlertSeverityHigh:
+          return SkColorSetRGB(0xf4, 0x34, 0x05);
+      }
+      return gfx::kPlaceholderColor;
+    }
+};
+
+FocusRingTheme* GetFocusRingTheme() {
+  static base::NoDestructor<FocusRingTheme> instance;
+  return instance.get();
+}
+
+}
+
+#define GetNativeTheme GetFocusRingTheme
+#include "../../../../ui/views/controls/focus_ring.cc"
+#undef GetNativeTheme