Fix flaky test on macOS

Author: nicerloop

shell/platform/common/flutter_platform_node_delegate_unittests.cc

@@ -236,7 +236,7 @@ TEST(FlutterPlatformNodeDelegateTest, canUseOwnerBridge) {
   auto child1_node = bridge->GetFlutterPlatformNodeDelegateFromID(1).lock();
   auto owner_bridge = child1_node->GetOwnerBridge().lock();
 
-  bool result;
+  bool result = false;
   gfx::RectF bounds = owner_bridge->RelativeToGlobalBounds(
       child1_node->GetAXNode(), result, true);
   EXPECT_EQ(bounds.x(), 0);