Fix tab strip rendering at non-integral scale factors in MD.

Fix tab strip rendering at non-integral scale factors in MD.

This fixes two issues:
* Hairline horizontal borders were actually drawing with thickness equal
  to the dsf for non-integral scale factors, due to loss of precision.
* The bottom of the tab fill path was not aligned with whole pixels,
  which was partially causing an artifact when ClipPath was called.

BUG=615153
Committed: https://crrev.com/a33441839f9a8d028db80a164891d32eaaf50b0b
Cr-Commit-Position: refs/heads/master@{#401171}

[Bret, 2016-06-21 22:12:30]

Description was changed from

==========
Fix tab strip rendering at non-integral scale factors in MD.

This fixes two issues:
* Hairline horizontal borders were actually drawing with thickness equal
  to the dsf for non-integral scale factors, due to loss of precision.
* The bottom of the tab fill path was not aligned with whole pixels,
  which was partially causing an artifact when ClipPath was called.

BUG=615153
==========

to

==========
Fix tab strip rendering at non-integral scale factors in MD.

This fixes two issues:
* Hairline horizontal borders were actually drawing with thickness equal
  to the dsf for non-integral scale factors, due to loss of precision.
* The bottom of the tab fill path was not aligned with whole pixels,
  which was partially causing an artifact when ClipPath was called.

BUG=615153
==========

[Bret, 2016-06-21 22:12:30]

bsep@chromium.org changed reviewers:
+ pkasting@chromium.org

[Peter Kasting, 2016-06-21 23:54:11]

LGTM

https://codereview.chromium.org/2085673004/diff/20001/chrome/browser/ui/views...
File chrome/browser/ui/views/tabs/tab.cc (right):

https://codereview.chromium.org/2085673004/diff/20001/chrome/browser/ui/views...
chrome/browser/ui/views/tabs/tab.cc:1659: const float bottom =
std::ceil(height() * scale);
Add a comment explaining this ceil() call as it's not obvious.

[Bret, 2016-06-22 01:00:48]

https://codereview.chromium.org/2085673004/diff/20001/chrome/browser/ui/views...
File chrome/browser/ui/views/tabs/tab.cc (right):

https://codereview.chromium.org/2085673004/diff/20001/chrome/browser/ui/views...
chrome/browser/ui/views/tabs/tab.cc:1659: const float bottom =
std::ceil(height() * scale);
On 2016/06/21 23:54:10, Peter Kasting wrote:
> Add a comment explaining this ceil() call as it's not obvious.

Done.

[Bret, 2016-06-22 01:00:51]

The CQ bit was checked by bsep@chromium.org

[Bret, 2016-06-22 01:00:51]

The patchset sent to the CQ was uploaded after l-g-t-m from
pkasting@chromium.org
Link to the patchset: https://codereview.chromium.org/2085673004/#ps40001
(title: "add comment")

[commit-bot: I haz the power, 2016-06-22 01:02:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2085673004/40001

[commit-bot: I haz the power, 2016-06-22 02:25:33]

Description was changed from

==========
Fix tab strip rendering at non-integral scale factors in MD.

This fixes two issues:
* Hairline horizontal borders were actually drawing with thickness equal
  to the dsf for non-integral scale factors, due to loss of precision.
* The bottom of the tab fill path was not aligned with whole pixels,
  which was partially causing an artifact when ClipPath was called.

BUG=615153
==========

to

==========
Fix tab strip rendering at non-integral scale factors in MD.

This fixes two issues:
* Hairline horizontal borders were actually drawing with thickness equal
  to the dsf for non-integral scale factors, due to loss of precision.
* The bottom of the tab fill path was not aligned with whole pixels,
  which was partially causing an artifact when ClipPath was called.

BUG=615153
==========

[commit-bot: I haz the power, 2016-06-22 02:25:34]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-06-22 02:28:14]

Description was changed from

==========
Fix tab strip rendering at non-integral scale factors in MD.

This fixes two issues:
* Hairline horizontal borders were actually drawing with thickness equal
  to the dsf for non-integral scale factors, due to loss of precision.
* The bottom of the tab fill path was not aligned with whole pixels,
  which was partially causing an artifact when ClipPath was called.

BUG=615153
==========

to

==========
Fix tab strip rendering at non-integral scale factors in MD.

This fixes two issues:
* Hairline horizontal borders were actually drawing with thickness equal
  to the dsf for non-integral scale factors, due to loss of precision.
* The bottom of the tab fill path was not aligned with whole pixels,
  which was partially causing an artifact when ClipPath was called.

BUG=615153

Committed: https://crrev.com/a33441839f9a8d028db80a164891d32eaaf50b0b
Cr-Commit-Position: refs/heads/master@{#401171}
==========

[commit-bot: I haz the power, 2016-06-22 02:28:15]

Patchset 3 (id:??) landed as
https://crrev.com/a33441839f9a8d028db80a164891d32eaaf50b0b
Cr-Commit-Position: refs/heads/master@{#401171}