Ensure that no scripts are resolved when compiling purely from deserialized data.

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 762e315d9979c2145465fa688ea0e7e136e5318d..4ee036fc0d5ef79a9d8327a248f8c7c5c8ea1a1e 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -322,7 +322,8 @@ abstract class Compiler implements LibraryLoaderListener {
       serialization = new SerializationTask(this),
       libraryLoader = new LibraryLoaderTask(
           resolvedUriTranslator,
-          new _ScriptLoader(this),
+          options.compileOnly
+              ? new _NoScriptLoader(this) : new _ScriptLoader(this),
           new _ElementScanner(scanner),
           serialization,
           this,
@@ -2165,6 +2166,18 @@ class _ScriptLoader implements ScriptLoader {
       compiler.readScript(uri, spannable);
 }
 
+/// [ScriptLoader] used to ensure that scripts are not loaded accidentally
+/// through the [LibraryLoader] when `CompilerOptions.compileOnly` is `true`.
+class _NoScriptLoader implements ScriptLoader {
+  Compiler compiler;
+  _NoScriptLoader(this.compiler);
+
+  Future<Script> readScript(Uri uri, [Spannable spannable]) {
+    compiler.reporter.internalError(spannable,
+        "Script loading of '$uri' is not enabled.");
+  }
+}
+
 class _ElementScanner implements ElementScanner {
   ScannerTask scanner;
   _ElementScanner(this.scanner);