Fix unreadable title text colour for PWA windows when GTK theme is used

This CL makes OpaqueBrowserFrameView test for whether the user is using
the system theme for the browser before using the hosted app theme
color algorithm.

This CL also updates the foreground color algorithm to always use the
actual frame color to avoid readability bugs like this in general.

Before: https://bugs.chromium.org/p/chromium/issues/attachment?aid=365224&signed_aid=05pRAK75RpeItQNbJQ32zA==&inline=1
After: https://bugs.chromium.org/p/chromium/issues/attachment?aid=365225&signed_aid=5PQmY9poCGVOGL8cIt7X3g==&inline=1
Change-Id: Id428054a636b408f59f88c49a0911f6a5052ccc5
Reviewed-on: https://chromium-review.googlesource.com/c/1307032Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604110}

chrome/browser/ui/views/frame/opaque_browser_frame_view.cc

@@ -639,14 +639,17 @@ bool OpaqueBrowserFrameView::ShouldShowWindowTitleBar() const {
 
 SkColor OpaqueBrowserFrameView::GetReadableFrameForegroundColor(
     ActiveState active_state) const {
+  const SkColor frame_color = GetFrameColor(active_state);
   if (browser_view()->IsBrowserTypeHostedApp()) {
-    base::Optional<SkColor> theme_color =
-        browser_view()->browser()->hosted_app_controller()->GetThemeColor();
-    if (theme_color)
-      return color_utils::GetThemedAssetColor(*theme_color);
+    const bool has_site_theme = browser_view()
+                                    ->browser()
+                                    ->hosted_app_controller()
+                                    ->GetThemeColor()
+                                    .has_value();
+    if (has_site_theme && !platform_observer_->IsUsingSystemTheme())
+      return color_utils::GetThemedAssetColor(frame_color);
   }
-  return color_utils::GetReadableColor(kTitleBarFeatureColor,
-                                       GetFrameColor(active_state));
+  return color_utils::GetReadableColor(kTitleBarFeatureColor, frame_color);
 }
 
 void OpaqueBrowserFrameView::PaintRestoredFrameBorder(

chrome/browser/ui/views/frame/opaque_browser_frame_view_browsertest.cc

@@ -7,6 +7,8 @@
 #include "base/test/scoped_feature_list.h"
 #include "build/build_config.h"
 #include "chrome/browser/extensions/browsertest_util.h"
+#include "chrome/browser/themes/theme_service.h"
+#include "chrome/browser/themes/theme_service_factory.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "chrome/browser/ui/views/frame/hosted_app_button_container.h"
@@ -83,6 +85,19 @@ IN_PROC_BROWSER_TEST_F(HostedAppOpaqueBrowserFrameViewTest, NoThemeColor) {
             SK_ColorBLACK);
 }
 
+#if defined(OS_LINUX) && !defined(OS_CHROMEOS)
+IN_PROC_BROWSER_TEST_F(HostedAppOpaqueBrowserFrameViewTest, SystemThemeColor) {
+  ThemeService* theme_service =
+      ThemeServiceFactory::GetForProfile(browser()->profile());
+  theme_service->UseSystemTheme();
+  ASSERT_TRUE(theme_service->UsingSystemTheme());
+  ASSERT_TRUE(InstallAndLaunchHostedApp(SK_ColorBLACK));
+
+  EXPECT_EQ(hosted_app_button_container_->active_color_for_testing(),
+            SK_ColorBLACK);
+}
+#endif  // defined(OS_LINUX) && !defined(OS_CHROMEOS)
+
 IN_PROC_BROWSER_TEST_F(HostedAppOpaqueBrowserFrameViewTest, LightThemeColor) {
   if (!InstallAndLaunchHostedApp(SK_ColorYELLOW))
     return;