Support the placeholder attribute on Android

Support the placeholder attribute on Android

Note: I still plan to refactor these so that more logic is shared between
the platforms, but it's nontrivial. In the meantime I think this is worth it
as long as it keeps improving the tests, because that will make the refactoring
that much less error-prone.

BUG=417104
Committed: https://crrev.com/c3e32b06c2f017310ab6c677e0c7b410c88455cb
Cr-Commit-Position: refs/heads/master@{#300706}

[dmazzoni, 2014-10-21 20:47:03]

dmazzoni@chromium.org changed reviewers:
+ plundblad@chromium.org

[Peter Lundblad, 2014-10-22 12:22:05]

lgtm

[dmazzoni, 2014-10-22 15:01:52]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2014-10-22 15:03:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/665333004/1

[commit-bot: I haz the power, 2014-10-22 18:08:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-22 18:09:26]

Patchset 1 (id:??) landed as
https://crrev.com/c3e32b06c2f017310ab6c677e0c7b410c88455cb
Cr-Commit-Position: refs/heads/master@{#300706}