MD Downloads: update "expanded" (i.e. in progress) cards

MD Downloads: update "expanded" (i.e. in progress) cards

1) Top-align file icons for progressing downloads
2) Remove progress rounded corners (not in new mocks, there were issues)

BUG=520728
R=groby@chromium.org

Committed: https://crrev.com/c547d4f8e8536241d535b699cff3a8c22be6016a
Cr-Commit-Position: refs/heads/master@{#344033}

[groby-ooo-7-16, 2015-08-18 18:25:02]

LGTM

[michaelpg, 2015-08-18 19:57:07]

https://codereview.chromium.org/1301723002/diff/20001/chrome/browser/resource...
File chrome/browser/resources/md_downloads/item.css (right):

https://codereview.chromium.org/1301723002/diff/20001/chrome/browser/resource...
chrome/browser/resources/md_downloads/item.css:42: border-radius: 2px;  /*
TODO(dbeam): why does this differ from Polymer? */
Unrelated to this CL, but at some point you can remove this TODO.

This differs because the demo styles the paper-material with a border-radius,
while the Polymer element itself does not.

paper-card has this border-radius by default.

[Dan Beam, 2015-08-18 20:41:12]

The CQ bit was checked by dbeam@chromium.org

[commit-bot: I haz the power, 2015-08-18 20:41:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1301723002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1301723002/20001

[commit-bot: I haz the power, 2015-08-18 21:18:33]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-08-18 21:19:05]

Patchset 2 (id:??) landed as
https://crrev.com/c547d4f8e8536241d535b699cff3a8c22be6016a
Cr-Commit-Position: refs/heads/master@{#344033}