cps-ir: Only use fallback compiler for platform functions.

pkg/compiler/lib/src/js_backend/codegen/task.dart

Index: pkg/compiler/lib/src/js_backend/codegen/task.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/task.dart b/pkg/compiler/lib/src/js_backend/codegen/task.dart
index fe6ecc60cdad334bbc8f8b46c22f5192d6a4a202..1573e82dc7499e08e76082a2fea01f54b266e8c0 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/task.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/task.dart
@@ -28,30 +28,28 @@ import '../../js_backend/codegen/codegen.dart';
 import '../../ssa/ssa.dart' as ssa;
 
 class CspFunctionCompiler implements FunctionCompiler {
-
-  // TODO(sigurdm): Assign this.
-  Tracer tracer;
-
-  String get name => 'CPS Ir pipeline';
-
   final IrBuilderTask irBuilderTask;
-
   final ConstantSystem constantSystem;
-
   final Compiler compiler;
 
-  // Remember to update dart-doc of [compile] when this field is removed.
+  // TODO(karlklose,sigurm): remove and update dart-doc of [compile].
   final FunctionCompiler fallbackCompiler;
 
+  // TODO(sigurdm): Assign this.
+  Tracer tracer;
+
   CspFunctionCompiler(Compiler compiler, JavaScriptBackend backend)
       : irBuilderTask = new IrBuilderTask(compiler),
         fallbackCompiler = new ssa.SsaFunctionCompiler(backend),
         constantSystem = backend.constantSystem,
         compiler = compiler;
 
+  String get name => 'CPS Ir pipeline';
+
   /// Generates JavaScript code for `work.element`. First tries to use the
   /// Cps Ir -> tree ir -> js pipeline, and if that fails due to language
-  /// features not implemented it will fall back to the ssa pipeline.
+  /// features not implemented it will fall back to the ssa pipeline (for
+  /// platform code) or will cancel compilation (for user code).
   js.Fun compile(CodegenWorkItem work) {
     AstElement element = work.element;
     return compiler.withCurrentElement(element, () {
@@ -65,9 +63,15 @@ class CspFunctionCompiler implements FunctionCompiler {
         treeFunction = optimizeTreeIR(treeFunction);
         return compileToJavaScript(work, treeFunction);
       } on CodegenBailout catch (e) {
-        compiler.log('Falling back to SSA compiler for $element'
-            ' (${e.message})');
-        return fallbackCompiler.compile(work);
+        if (element.library.isPlatformLibrary) {
+          compiler.log('Falling back to SSA compiler for $element'
+              ' (${e.message})');
+          return fallbackCompiler.compile(work);
+        } else {
+          String message = "Unable to compile $element with the new compiler.\n"
+              "  Reason: ${e.message}";
+          compiler.internalError(element, message);
+        }
       }
     });
   }