Don't force non-incognito default colors for X11/increased contrast themes.

For X11 this likely doesn't matter, as in practice NativeThemeGtk::GetColor()
will probably override everything.  For the increased contrast theme supplier,
someday we probably want to replace this with better platform-native high
contrast support on the platforms that use it, but for now, it doesn't make
sense to disable incognito default colors in most cases; the code in question
was only intended to apply to custom themes.

This _does_ still apply "force non-incognito" to autogenerated themes, since
these should basically work "like custom themes" as much as possible.  If we
wanted, we could likely change this by ensuring the autogenerator overrides
everything necessary.  I don't have a strong opinion.

This is primarily a set-up change for fixing bug 621004, by exposing a method
that we'll also use to control "disable dark mode".

Bug: 621004
Change-Id: I6375cea9ae88d56a02c212258caf3b647af30585
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1938569
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Gayane Petrosyan <gayane@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719713}

chrome/browser/themes/theme_service.cc

@@ -475,6 +475,10 @@ bool ThemeService::UsingAutogeneratedTheme() const {
   return autogenerated;
 }
 
+bool ThemeService::ForceLightDefaultColors() const {
+  return UsingExtensionTheme() || UsingAutogeneratedTheme();
+}
+
 std::string ThemeService::GetThemeID() const {
   return profile_->GetPrefs()->GetString(prefs::kCurrentThemeID);
 }
@@ -658,10 +662,7 @@ SkColor ThemeService::GetDefaultColor(int id, bool incognito) const {
     }
   }
 
-  // Always fall back to the non-incognito color when there's a custom theme
-  // because the default (classic) incognito color may be dramatically different
-  // (optimized for a light-on-dark color).
-  return TP::GetDefaultColor(id, incognito && !theme_supplier_);
+  return TP::GetDefaultColor(id, incognito && !ForceLightDefaultColors());
 }
 
 color_utils::HSL ThemeService::GetTint(int id, bool incognito) const {
@@ -671,9 +672,7 @@ color_utils::HSL ThemeService::GetTint(int id, bool incognito) const {
   if (theme_supplier_ && theme_supplier_->GetTint(id, &hsl))
     return hsl;
 
-  // Always fall back to the non-incognito tint when there's a custom theme.
-  // See comment in GetDefaultColor().
-  return TP::GetDefaultTint(id, incognito && !theme_supplier_);
+  return TP::GetDefaultTint(id, incognito && !ForceLightDefaultColors());
 }
 
 void ThemeService::ClearAllThemeData() {

chrome/browser/themes/theme_service.h

@@ -128,6 +128,10 @@ class ThemeService : public content::NotificationObserver,
   // Whether we are using an autogenerated theme.
   virtual bool UsingAutogeneratedTheme() const;
 
+  // Whether to force the use of light colors/tints by default, i.e. ignore
+  // incognito state.  This is true for extension and autogenerated themes.
+  bool ForceLightDefaultColors() const;
+
   // Gets the id of the last installed theme. (The theme may have been further
   // locally customized.)
   virtual std::string GetThemeID() const;