Formalizing the hacks letting the angular analyzer plugin run for now.

pkg/analyzer/lib/src/context/builder.dart

Index: pkg/analyzer/lib/src/context/builder.dart
diff --git a/pkg/analyzer/lib/src/context/builder.dart b/pkg/analyzer/lib/src/context/builder.dart
index 0bd531e4e9e197ddc57593fad45b9cafe9a96c34..a3e899b0922aee6f0b29e9ef58f9b3ef9c11e1c1 100644
--- a/pkg/analyzer/lib/src/context/builder.dart
+++ b/pkg/analyzer/lib/src/context/builder.dart
@@ -60,6 +60,14 @@ import 'package:yaml/yaml.dart';
  */
 class ContextBuilder {
   /**
+   * A callback for when analysis drivers are created, which takes all the same
+   * arguments as the dart analysis driver constructor so that plugins may
+   * create their own drivers with the same tools, in theory. Here as a stopgap
+   * until the official plugin API is complete
+   */
+  static Function onCreateAnalysisDriver = null;
+
+  /**
    * The [ResourceProvider] by which paths are converted into [Resource]s.
    */
   final ResourceProvider resourceProvider;
@@ -149,6 +157,7 @@ class ContextBuilder {
   AnalysisDriver buildDriver(String path) {
     AnalysisOptions options = getAnalysisOptions(path);
     //_processAnalysisOptions(context, optionMap);
+    final sf = createSourceFactory(path, options);
     AnalysisDriver driver = new AnalysisDriver(
         analysisDriverScheduler,
         performanceLog,
@@ -156,8 +165,13 @@ class ContextBuilder {
         byteStore,
         fileContentOverlay,
         path,
-        createSourceFactory(path, options),
+        sf,
         options);
+    // temporary plugin support:
+    if (onCreateAnalysisDriver != null) {
+      onCreateAnalysisDriver(driver, analysisDriverScheduler, performanceLog,
+          resourceProvider, byteStore, fileContentOverlay, path, sf, options);
+    }
     declareVariablesInDriver(driver);
     return driver;
   }