Return the width of a placeholder in iterateThroughSingleRunByStyles

Also avoid visiting the text run that contains the placeholder
character.

See https://github.com/flutter/flutter/issues/104077

Change-Id: I1c9792f165c7fa971dbf13ba3130f1a787065d0d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/541790
Reviewed-by: Julia Lavrova <jlavrova@google.com>
Commit-Queue: Jason Simmons <jsimmons@google.com>
1 file changed