Revert "Add support for 'dart.library.X' environment variables in dart2js."

pkg/compiler/lib/src/apiimpl.dart

Index: pkg/compiler/lib/src/apiimpl.dart
diff --git a/pkg/compiler/lib/src/apiimpl.dart b/pkg/compiler/lib/src/apiimpl.dart
index e84777f59200c13be55ae623671dc2bbc1e23be2..8f81d151dcce9e238914c8b690bb1013e1e5b3d2 100644
--- a/pkg/compiler/lib/src/apiimpl.dart
+++ b/pkg/compiler/lib/src/apiimpl.dart
@@ -33,14 +33,6 @@ import 'script.dart';
 const bool forceIncrementalSupport =
     const bool.fromEnvironment('DART2JS_EXPERIMENTAL_INCREMENTAL_SUPPORT');
 
-/// For every 'dart:' library, a corresponding environment variable is set
-/// to "true". The environment variable's name is the concatenation of
-/// this prefix and the name (without the 'dart:'.
-///
-/// For example 'dart:html' has the environment variable 'dart.library.html' set
-/// to "true".
-const String dartLibraryEnvironmentPrefix = 'dart.library.';
-
 /// Locations of the platform descriptor files relative to the library root.
 const String _clientPlatform = "lib/dart_client.platform";
 const String _serverPlatform = "lib/dart_server.platform";
@@ -588,26 +580,7 @@ class CompilerImpl extends Compiler {
     }
   }
 
-  fromEnvironment(String name) {
-    assert(invariant(NO_LOCATION_SPANNABLE,
-        sdkLibraries != null, message: "setupSdk() has not been run"));
-
-    var result = environment[name];
-    if (result != null || environment.containsKey(name)) return result;
-    if (!name.startsWith(dartLibraryEnvironmentPrefix)) return null;
-
-    String libraryName = name.substring(dartLibraryEnvironmentPrefix.length);
-    if (sdkLibraries.containsKey(libraryName)) {
-      // Dart2js always "supports" importing 'dart:mirrors' but will abort
-      // the compilation at a later point if the backend doesn't support
-      // mirrors. In this case 'mirrors' should not be in the environment.
-      if (name == dartLibraryEnvironmentPrefix + 'mirrors') {
-        return backend.supportsReflection ? "true" : null;
-      }
-      return "true";
-    }
-    return null;
-  }
+  fromEnvironment(String name) => environment[name];
 
   Uri lookupLibraryUri(String libraryName) {
     assert(invariant(NO_LOCATION_SPANNABLE,