Fix bug on Android causing composition underlines to appear in the wrong place

Fix bug on Android causing composition underlines to appear in the wrong place

The previous code I introduced in DocumentMarkerController::setComposition()
was passing an offset measured in DOM children to addCompositionUnderlines()
(and it wasn't even measured correctly) when it should have been passing an
offset measured in plain text characters. Oops

I'd like to add a test case for this bug, unfortunately I'm having trouble
reproducing it in a test.

BUG=692699
Review-Url: https://codereview.chromium.org/2689233006
Cr-Commit-Position: refs/heads/master@{#451903}
(cherry picked from commit 6923513dcedf4c6b55bc923fc0146aff71b3da46)

Review-Url: https://codereview.chromium.org/2709343002 .
Cr-Commit-Position: refs/branch-heads/2987@{#646}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/21aa8273bfcc29e0a7048213f667a0542451fa8c

[aelias_OOO_until_Jul13, 2017-02-22 22:07:13]

Description was changed from

==========
Fix bug on Android causing composition underlines to appear in the wrong place

The previous code I introduced in DocumentMarkerController::setComposition()
was passing an offset measured in DOM children to addCompositionUnderlines()
(and it wasn't even measured correctly) when it should have been passing an
offset measured in plain text characters. Oops

I'd like to add a test case for this bug, unfortunately I'm having trouble
reproducing it in a test.

BUG=692699

Review-Url: https://codereview.chromium.org/2689233006
Cr-Commit-Position: refs/heads/master@{#451903}
(cherry picked from commit 6923513dcedf4c6b55bc923fc0146aff71b3da46)
==========

to

==========
Fix bug on Android causing composition underlines to appear in the wrong place

The previous code I introduced in DocumentMarkerController::setComposition()
was passing an offset measured in DOM children to addCompositionUnderlines()
(and it wasn't even measured correctly) when it should have been passing an
offset measured in plain text characters. Oops

I'd like to add a test case for this bug, unfortunately I'm having trouble
reproducing it in a test.

BUG=692699

Review-Url: https://codereview.chromium.org/2689233006
Cr-Commit-Position: refs/heads/master@{#451903}
(cherry picked from commit 6923513dcedf4c6b55bc923fc0146aff71b3da46)

Review-Url: https://codereview.chromium.org/2709343002 .
Cr-Commit-Position: refs/branch-heads/2987@{#646}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/21aa8273bfcc29e0a7048213f667...
==========

[aelias_OOO_until_Jul13, 2017-02-22 22:07:14]

Committed patchset #1 (id:1) manually as
21aa8273bfcc29e0a7048213f667a0542451fa8c.