Run dartfmt on all files under runtime.

runtime/observatory/tests/observatory_ui/mocks/objects/persistent_handles.dart

Index: runtime/observatory/tests/observatory_ui/mocks/objects/persistent_handles.dart
diff --git a/runtime/observatory/tests/observatory_ui/mocks/objects/persistent_handles.dart b/runtime/observatory/tests/observatory_ui/mocks/objects/persistent_handles.dart
index 5e65785655e431bb9fd986929d2d4b8166709cb1..692644982abd519c1266502d7a8786df28e8f270 100644
--- a/runtime/observatory/tests/observatory_ui/mocks/objects/persistent_handles.dart
+++ b/runtime/observatory/tests/observatory_ui/mocks/objects/persistent_handles.dart
@@ -8,8 +8,8 @@ class PersistentHandlesMock implements M.PersistentHandles {
   final Iterable<M.PersistentHandle> elements;
   final Iterable<M.WeakPersistentHandle> weakElements;
 
-  const PersistentHandlesMock({this.elements: const [],
-                               this.weakElements: const []});
+  const PersistentHandlesMock(
+      {this.elements: const [], this.weakElements: const []});
 }
 
 class PersistentHandleMock implements M.PersistentHandle {
@@ -25,8 +25,10 @@ class WeakPersistentHandleMock implements M.WeakPersistentHandle {
   final String callbackSymbolName;
   final String callbackAddress;
 
-  const WeakPersistentHandleMock({this.object: const InstanceRefMock(),
-                                  this.externalSize: 0, this.peer: '0x0',
-                                  this.callbackSymbolName: 'dart::Something()',
-                                  this.callbackAddress: '0x123456'});
+  const WeakPersistentHandleMock(
+      {this.object: const InstanceRefMock(),
+      this.externalSize: 0,
+      this.peer: '0x0',
+      this.callbackSymbolName: 'dart::Something()',
+      this.callbackAddress: '0x123456'});
 }