Use getAttribute to sample 'd' attribute in interpolation-test.js

Use getAttribute to sample 'd' attribute in interpolation-test.js

pathSegList is going away, so use getAttribute('d') instead.
Adjust some expectations - mostly for 'z' vs 'Z' (not possible to
discern after parsing.)

BUG=539385
Committed: https://crrev.com/2c4120b77968ad3825101ed287726575b87ef8d8
Cr-Commit-Position: refs/heads/master@{#355476}

[fs, 2015-10-21 19:24:49]

fs@opera.com changed reviewers:
+ ericwilligers@chromium.org

[Eric Willigers, 2015-10-22 01:51:06]

The CQ bit was checked by ericwilligers@chromium.org

[Eric Willigers, 2015-10-22 01:51:07]

lgtm

[commit-bot: I haz the power, 2015-10-22 01:52:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1417103003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1417103003/1

[commit-bot: I haz the power, 2015-10-22 01:56:53]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-22 01:57:50]

Patchset 1 (id:??) landed as
https://crrev.com/2c4120b77968ad3825101ed287726575b87ef8d8
Cr-Commit-Position: refs/heads/master@{#355476}