Add command-line parameter enabling assert messages.

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index ef2a0b3e1b7902b5d2186d1be40ca91c482d0b9b..127d87fc48f123e5eec20be6d2b0a1c191cd0129 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -188,6 +188,7 @@ abstract class Compiler implements DiagnosticListener {
   final bool dumpInfo;
   final bool useContentSecurityPolicy;
   final bool enableExperimentalMirrors;
+  final bool allowAssertMessage;
 
   /**
    * The maximum size of a concrete type before it widens to dynamic during
@@ -519,7 +520,8 @@ abstract class Compiler implements DiagnosticListener {
             this.generateCodeWithCompileTimeErrors: false,
             this.testMode: false,
             api.CompilerOutput outputProvider,
-            List<String> strips: const []})
+            List<String> strips: const [],
+            this.allowAssertMessage: false})
       : this.disableTypeInferenceFlag =
           disableTypeInferenceFlag || !emitJavaScript,
         this.analyzeOnly =
@@ -530,6 +532,7 @@ abstract class Compiler implements DiagnosticListener {
         cacheStrategy = new CacheStrategy(hasIncrementalSupport),
         this.userOutputProvider = outputProvider == null
             ? const NullCompilerOutput() : outputProvider {
+    print("COMPILER: $allowAssertMessage");
     if (hasIncrementalSupport) {
       // TODO(ahe): This is too much. Any method from platform and package
       // libraries can be inlined.