libtxt: remove obsolete font_manager_available defines (#9376)

third_party/txt/BUILD.gn

@@ -26,14 +26,9 @@ config("txt_config") {
 }
 
 source_set("txt") {
-  if (current_toolchain == host_toolchain && !is_mac) {
-    defines = [ "DIRECTORY_FONT_MANAGER_AVAILABLE" ]
-  }
-  if (is_android) {
-    defines = [ "ANDROID_FONT_MANAGER_AVAILABLE" ]
-  }
+  defines = []
   if (flutter_use_fontconfig) {
-    defines = [ "FONTCONFIG_FONT_MANAGER_AVAILABLE" ]
+    defines += [ "FLUTTER_USE_FONTCONFIG" ]
   }
 
   sources = [

third_party/txt/src/txt/platform_linux.cc

@@ -4,7 +4,7 @@
 
 #include "txt/platform.h"
 
-#ifdef FONTCONFIG_FONT_MANAGER_AVAILABLE
+#ifdef FLUTTER_USE_FONTCONFIG
 #include "third_party/skia/include/ports/SkFontMgr_fontconfig.h"
 #else
 #include "third_party/skia/include/ports/SkFontMgr_directory.h"
@@ -17,7 +17,7 @@ std::string GetDefaultFontFamily() {
 }
 
 sk_sp<SkFontMgr> GetDefaultFontManager() {
-#ifdef FONTCONFIG_FONT_MANAGER_AVAILABLE
+#ifdef FLUTTER_USE_FONTCONFIG
   return SkFontMgr_New_FontConfig(nullptr);
 #else
   return SkFontMgr_New_Custom_Directory("/usr/share/fonts/");