[dart:io] Move Platform.ansiSupported to {Stdin,Stdout}.supportsAnsiEscapes

sdk/lib/io/platform.dart

Index: sdk/lib/io/platform.dart
diff --git a/sdk/lib/io/platform.dart b/sdk/lib/io/platform.dart
index 482898c8d01a007b68d5a8b9a7de8718301e28fb..b087b053c3203fba77c7cf37c961a5fb0bfb1bae 100644
--- a/sdk/lib/io/platform.dart
+++ b/sdk/lib/io/platform.dart
@@ -71,7 +71,6 @@ class Platform {
   static final _operatingSystem = _Platform.operatingSystem;
   static final _localHostname = _Platform.localHostname;
   static final _version = _Platform.version;
-  static final _ansiSupported = _Platform.ansiSupported;
 
   /**
    * Get the number of processors of the machine.
@@ -126,14 +125,6 @@ class Platform {
   static final bool isFuchsia = (_operatingSystem == "fuchsia");
 
   /**
-    * When stdio is connected to a terminal, whether ANSI codes are supported.
-    *
-    * This value is hard-coded to `true`, except on Windows where only more
-    * recent versions of Windows 10 support the codes.
-    */
-  static final bool ansiSupported = _ansiSupported;
-
-  /**
    * Get the environment for this process.
    *
    * The returned environment is an unmodifiable map which content is