Bucket the physical device pixel ratio to the nearest 0.5 while viewport
emulation is active and retain the selected value for the Page lifetime.
Expose the same protected DPR through window.devicePixelRatio and CSS
resolution media queries. This prevents the physical value from leaking
through either API and avoids inconsistencies between JavaScript and CSS.
Include the viewport-emulation scale when converting the virtual keyboard
overlay rectangle, keeping its geometry in the same emulated coordinate
space.
Test: Verified on Android that a physical DPR of 3.8 is exposed as 4
through window.devicePixelRatio and resolution media queries.
Carmelo Messina
40c0283e1e