Add support for compiling Dart via the FE 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 1620fda6cfb0d8f377bd46f2a1167c860098bf98..c951790dcb67c7c178c15d721f4cf79d256caf29 100644
--- a/pkg/compiler/lib/src/apiimpl.dart
+++ b/pkg/compiler/lib/src/apiimpl.dart
@@ -139,7 +139,7 @@ class CompilerImpl extends Compiler {
     if (!resourceUri.isAbsolute) {
       if (node == null) node = NO_LOCATION_SPANNABLE;
       reporter.internalError(
-          node, 'Relative uri $resourceUri provided to readScript(Uri).');
+          node, 'Relative uri $resourceUri provided to readBinary(Uri).');
     }
 
     // We need to store the current element since we are reporting read errors