Revert "Set correct pixel size for the compositor"

This reverts commit c1a826ab79d4303ddd87bbbf4f6d38995c4bcd36.

Reason for revert: Screen stops updating on some devices with non default scale factor

Bug: 866010

Original change's description:
> Set correct pixel size for the compositor
> Right now we clip(GL_SCISSOR) the display buffer based on the physical
> pixel size of the display. The pixel size we send to the ui compositor
> is the size we receive from the platform window(the display in Chrome
> OS). However, this may not be what we want if the platform has some
> fractional scale applied.
> UI elements have their sizes set in DIP. If some UI element (ui::Layer)
> has its size set to the DIP size of the display, their scaled size
> (the pixel size after applying device scale factor) after rounding may
> not match the physical pixel size of the display. This difference may
> lead to 1px lines left unclipped. This happens in the case of the shelf
> whose width is set to the width of the display. For a device like eve
> where the internal display has a physical resolution width of 2400px,
> if a device scale of 1.8 is applied, the DIP width of the display
> becomes 1333. We set the bounds of the shelf to this. Now when we do
> the actual paint, we scale the shelf to its physical pixel size which
> is ROUND(1333*1.8) = 2399. At the same time the compositor will clip
> things at width 2400. This difference is what gives the shelf a 1px
> gap.
> A proper way to fix this is to scale ui::Layer bounds such that it
> snaps to the parent's or displays edge similar to what pixel canvas
> does in views::View. However, that is a large change. In the meantime
> this patch sets the correct physical pixel size for the compositor so
> that correct clipping happens.
> Bug: 843354
> Change-Id: Ic9e055c0ba39d85a7297809baf946398bf09f40a
> Component: UI compositor, pixel canvas, scaling, HiDPI
> Reviewed-on:
> Reviewed-by: Mitsuru Oshima <>
> Reviewed-by: Nico Weber <>
> Commit-Queue: Malay Keshav <>
> Cr-Commit-Position: refs/heads/master@{#575402},,

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 843354
Change-Id: If6d8e5649f37ec2cece1411419ca2db61daf06c8
Reviewed-by: Michael Spang <>
Commit-Queue: Michael Spang <>
Cr-Commit-Position: refs/heads/master@{#578042}
4 files changed