Enforce marking "override" for functions overriding Blink in components/test_runner/.

components/test_runner/mock_color_chooser.h

Index: components/test_runner/mock_color_chooser.h
diff --git a/components/test_runner/mock_color_chooser.h b/components/test_runner/mock_color_chooser.h
index 4656d9bbd14a1db6c2991a5976a3c0e5d16418d8..74af942b11b1ebe206ed33ca3a47d3ce1068b6d9 100644
--- a/components/test_runner/mock_color_chooser.h
+++ b/components/test_runner/mock_color_chooser.h
@@ -20,11 +20,11 @@ public:
     MockColorChooser(blink::WebColorChooserClient* client,
                      WebTestDelegate* delegate,
                      WebTestProxyBase* proxy);
-    virtual ~MockColorChooser();
+    ~MockColorChooser() override;
 
     // blink::WebColorChooser implementation.
-    virtual void setSelectedColor(const blink::WebColor color) override;
-    virtual void endChooser() override;
+    void setSelectedColor(const blink::WebColor color) override;
+    void endChooser() override;
 
     void InvokeDidEndChooser();
     WebTaskList* mutable_task_list() { return &task_list_; }