MD downloads: add a narrow mode for smaller windows

MD downloads: add a narrow mode for smaller windows

- Drops date separator lines
- Moves dates on top of download items (instead of next to)
- Moves actions into a <paper-menu-button> next to search

BUG=425626
R=tommycli@chromium.org

Committed: https://crrev.com/453aef33b68d80111b35da2ddc69a9a2b4910c5e
Cr-Commit-Position: refs/heads/master@{#341416}

[Dan Beam, 2015-07-31 01:09:30]

Patchset #2 (id:20001) has been deleted

[Dan Beam, 2015-07-31 01:09:35]

Patchset #1 (id:1) has been deleted

[Dan Beam, 2015-07-31 01:13:54]

Patchset #1 (id:40001) has been deleted

[Dan Beam, 2015-07-31 01:22:48]

Patchset #1 (id:60001) has been deleted

[tommycli, 2015-07-31 17:54:57]

lgtm sans below

https://codereview.chromium.org/1265683003/diff/80001/chrome/browser/resource...
File chrome/browser/resources/md_downloads/item.css (right):

https://codereview.chromium.org/1265683003/diff/80001/chrome/browser/resource...
chrome/browser/resources/md_downloads/item.css:51: @media all and (max-width:
1024px) {
Should be adjacent to the opposite media query

[Dan Beam, 2015-07-31 18:36:37]

https://codereview.chromium.org/1265683003/diff/80001/chrome/browser/resource...
File chrome/browser/resources/md_downloads/item.css (right):

https://codereview.chromium.org/1265683003/diff/80001/chrome/browser/resource...
chrome/browser/resources/md_downloads/item.css:51: @media all and (max-width:
1024px) {
On 2015/07/31 17:54:56, tommycli wrote:
> Should be adjacent to the opposite media query

Done.

[Dan Beam, 2015-07-31 21:30:35]

The CQ bit was checked by dbeam@chromium.org

[Dan Beam, 2015-07-31 21:30:36]

The patchset sent to the CQ was uploaded after l-g-t-m from
tommycli@chromium.org
Link to the patchset: https://codereview.chromium.org/1265683003/#ps100001
(title: "tommycli@ review")

[commit-bot: I haz the power, 2015-07-31 21:30:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1265683003/100001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1265683003/100001

[commit-bot: I haz the power, 2015-07-31 21:36:53]

Committed patchset #2 (id:100001)

[commit-bot: I haz the power, 2015-07-31 21:37:23]

Patchset 2 (id:??) landed as
https://crrev.com/453aef33b68d80111b35da2ddc69a9a2b4910c5e
Cr-Commit-Position: refs/heads/master@{#341416}