Just set borders once when creating a views::LabelButton

chrome/test/base/view_event_test_base.h

Index: chrome/test/base/view_event_test_base.h
diff --git a/chrome/test/base/view_event_test_base.h b/chrome/test/base/view_event_test_base.h
index 21188d23c4bd758a7c98ab9fa59220b8ba501927..5629c38b28c2737b2d193f64b9c767fb40518931 100644
--- a/chrome/test/base/view_event_test_base.h
+++ b/chrome/test/base/view_event_test_base.h
@@ -85,6 +85,11 @@ class ViewEventTestBase : public views::WidgetDelegate,
   // Destroys the window.
   void TearDown() override;
 
+  // Returns an empty Size. Subclasses that want a preferred size other than
+  // that of the View returned by CreateContentsView should override this
+  // appropriately.
+  virtual gfx::Size GetPreferredSize() const;
+
   // Overridden from views::WidgetDelegate:
   bool CanResize() const override;
   views::View* GetContentsView() override;
@@ -108,11 +113,6 @@ class ViewEventTestBase : public views::WidgetDelegate,
   // schedules a task that invokes DoTestOnMessageLoop.
   void StartMessageLoopAndRunTest();
 
-  // Returns an empty Size. Subclasses that want a preferred size other than
-  // that of the View returned by CreateContentsView should override this
-  // appropriately.
-  virtual gfx::Size GetPreferredSize() const;
-
   // Creates a task that calls the specified method back. The specified
   // method is called in such a way that if there are any test failures
   // Done is invoked.