Enable strict-virtual-specifiers for iOS builds.

ui/gfx/image/image_ios_unittest.mm

Index: ui/gfx/image/image_ios_unittest.mm
diff --git a/ui/gfx/image/image_ios_unittest.mm b/ui/gfx/image/image_ios_unittest.mm
index 789fe72cade431e31b683a90ab9b708e423a00b1..a9558b0381d12562b400175bd75394399fafc1b1 100644
--- a/ui/gfx/image/image_ios_unittest.mm
+++ b/ui/gfx/image/image_ios_unittest.mm
@@ -46,13 +46,13 @@ UIImage* UIImageWithSizeAndScale(CGFloat width, CGFloat height, CGFloat scale) {
 class ImageIOSTest : public testing::Test {
  public:
   ImageIOSTest() {}
-  virtual ~ImageIOSTest() {}
+  ~ImageIOSTest() override {}
 
-  virtual void SetUp() override {
+  void SetUp() override {
     original_scale_factors_ = gfx::ImageSkia::GetSupportedScales();
   }
 
-  virtual void TearDown() override {
+  void TearDown() override {
     gfx::ImageSkia::SetSupportedScales(original_scale_factors_);
   }