Dispose AnalysisContext(s) used to resynthesize CompilationUnitElement(s) for IndexResult(s).

pkg/analyzer/lib/src/dart/analysis/driver.dart

Index: pkg/analyzer/lib/src/dart/analysis/driver.dart
diff --git a/pkg/analyzer/lib/src/dart/analysis/driver.dart b/pkg/analyzer/lib/src/dart/analysis/driver.dart
index 7d493d612f89a16d6e64bca07cd4048013e30528..ecf4de5e3f2a850e13266307fcf3c0b70868ace3 100644
--- a/pkg/analyzer/lib/src/dart/analysis/driver.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/driver.dart
@@ -592,9 +592,14 @@ class AnalysisDriver {
     AnalysisContext analysisContext = _createAnalysisContext(libraryContext);
 
     // Resynthesize the CompilationUnitElement in the context.
-    CompilationUnitElement unitElement = analysisContext.computeResult(
-        new LibrarySpecificUnit(libraryFile.source, file.source),
-        COMPILATION_UNIT_ELEMENT);
+    CompilationUnitElement unitElement;
+    try {
+      unitElement = analysisContext.computeResult(
+          new LibrarySpecificUnit(libraryFile.source, file.source),
+          COMPILATION_UNIT_ELEMENT);
+    } finally {
+      analysisContext.dispose();
+    }
 
     // Return as IndexResult.
     return new IndexResult(unitElement, analysisResult._index);