To reproduce: 1. Go to data:text/html,%3Cselect%3E%3Coption%3ECompare%20the%20height%20of%20this%3C/select%3E%3Cbutton%3E...to%20this%20(and%20try%20pressing%20me!) The button is taller than the <select>, but shouldn't be. When the button is pressed, its height shrinks to match the <select>. The button also looks a little blurry when un-pressed (perhaps because it's stretched?).
<rdar://problem/10085061>
Strangely, I can no longer reproduce this.
But I can! reopening.
I can reproduce problems when the page is scaled via the Page::scalePage() api to zoomed via command-shift-+ in Safari. However, I cannot reproduce any problems when changed the HiDPI scale factor in System Preferences, so I am removing the phrase "HiDPI" from the title.