Normalize URIs on entry to ValidatingInstrumentation.

pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
index 587fd496fcd17670c498fb1b70fa808dea8e82d3..ffe3b5e2476fe564f8ab1cfb27b2222635cf9ed6 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
@@ -498,14 +498,6 @@ class KernelField extends Field {
     super.type = value;
   }
 
-  String get _fileUri {
-    // TODO(paulberry): This is a hack.  We should use this.fileUri, because we
-    // want the URI of the compilation unit.  But that gives a relative URI,
-    // and I don't know what it's relative to or how to convert it to an
-    // absolute URI.
-    return enclosingLibrary.importUri.toString();
-  }
-
   void _setInferredType(DartType inferredType) {
     _isInferred = true;
     super.type = inferredType;
@@ -1558,7 +1550,7 @@ class KernelTypeInferenceEngine extends TypeInferenceEngineImpl {
   KernelTypeInferrer createTopLevelTypeInferrer(
       KernelField field, TypeInferenceListener listener) {
     return field._typeInferrer =
-        new KernelTypeInferrer._(this, getFieldUri(field), listener, true);
+        new KernelTypeInferrer._(this, field.fileUri, listener, true);
   }
 
   @override
@@ -1582,11 +1574,6 @@ class KernelTypeInferenceEngine extends TypeInferenceEngineImpl {
   }
 
   @override
-  String getFieldUri(KernelField field) {
-    return field._fileUri;
-  }
-
-  @override
   bool isFieldInferred(KernelField field) {
     return field._isInferred;
   }