Make gfx::Rect class operations consistently mutate the class they are called on.

ui/base/native_theme/native_theme_base.cc

Index: ui/base/native_theme/native_theme_base.cc
diff --git a/ui/base/native_theme/native_theme_base.cc b/ui/base/native_theme/native_theme_base.cc
index 96c4a3c21f849a7e74bbe0f88b8a0061df4b984d..df9b7bf93ca9acef7ec9c66fe7b357f60eff3811 100644
--- a/ui/base/native_theme/native_theme_base.cc
+++ b/ui/base/native_theme/native_theme_base.cc
@@ -504,7 +504,8 @@ void NativeThemeBase::PaintCheckbox(SkCanvas* canvas,
         rb.GetImageSkiaNamed(IDR_CHECKBOX_OFF);
   }
 
-  gfx::Rect bounds = rect.Center(gfx::Size(image->width(), image->height()));
+  gfx::Rect bounds = rect;
+  bounds.ClampToCenteredSize(gfx::Size(image->width(), image->height()));
   DrawImageInt(canvas, *image, 0, 0, image->width(), image->height(),
       bounds.x(), bounds.y(), bounds.width(), bounds.height());
 }
@@ -655,7 +656,8 @@ void NativeThemeBase::PaintRadio(SkCanvas* canvas,
         rb.GetImageSkiaNamed(IDR_RADIO_OFF);
   }
 
-  gfx::Rect bounds = rect.Center(gfx::Size(image->width(), image->height()));
+  gfx::Rect bounds = rect;
+  bounds.ClampToCenteredSize(gfx::Size(image->width(), image->height()));
   DrawImageInt(canvas, *image, 0, 0, image->width(), image->height(),
       bounds.x(), bounds.y(), bounds.width(), bounds.height());
 }