- Fix usage of Platform.packageRoot.

pkg/analyzer/tool/task_dependency_graph/generate.dart

Index: pkg/analyzer/tool/task_dependency_graph/generate.dart
diff --git a/pkg/analyzer/tool/task_dependency_graph/generate.dart b/pkg/analyzer/tool/task_dependency_graph/generate.dart
index 4ae30faf0657aefa29d509302c3e39576193c6b3..91560b27ce17d7284917174a83ed981ffba3f279 100644
--- a/pkg/analyzer/tool/task_dependency_graph/generate.dart
+++ b/pkg/analyzer/tool/task_dependency_graph/generate.dart
@@ -128,7 +128,8 @@ class Driver {
     context = AnalysisEngine.instance.createAnalysisContext();
     String packageRootPath;
     if (Platform.packageRoot.isNotEmpty) {
-      packageRootPath = Platform.packageRoot;
+      Uri packageRootUri = Uri.parse(Platform.packageRoot);
+      packageRootPath = packageRootUri.toFilePath();
     } else {
       packageRootPath = path.join(rootDir, 'packages');
     }