Revert of Revert of Set the javac target and source to 1.7

Revert of Revert of Set the javac target and source to 1.7 (patchset #1 id:1 of https://chromiumcodereview.appspot.com/579543003/)

Reason for revert:
All the bots have been switched to Java 7 according to https://code.google.com/p/chromium/issues/detail?id=411503#c19

Original issue's description:
> Revert of Set the javac target and source to 1.7 (patchset #2 id:20001 of https://chromiumcodereview.appspot.com/545363002/)
>
> Reason for revert:
> Not all bots have Java 7 yet :(
>
> Original issue's description:
> > Set the javac target and source to 1.7
> >
> > BUG=336589
> > TBR=yfriedman@chromium.org
> >
> > Committed: https://crrev.com/165c0f17fe5760a3f346940d4fb2574d62cfe53b
> > Cr-Commit-Position: refs/heads/master@{#295162}
>
> TBR=cjhopman@chromium.org,yfriedman@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=336589
>
> Committed: https://crrev.com/094138696e943744d1489ebb98276b116eafed99
> Cr-Commit-Position: refs/heads/master@{#295165}

TBR=cjhopman@chromium.org,yfriedman@chromium.org
BUG=336589
Committed: https://crrev.com/119c6fa8247481d2e36910d30175d0214fd2ece5
Cr-Commit-Position: refs/heads/master@{#296630}

[aurimas (slooooooooow), 2014-09-25 01:23:56]

Created Revert of Revert of Set the javac target and source to 1.7

[aurimas (slooooooooow), 2014-09-25 01:24:15]

The CQ bit was unchecked by aurimas@chromium.org

[aurimas (slooooooooow), 2014-09-25 01:24:32]

The CQ bit was checked by aurimas@chromium.org

[commit-bot: I haz the power, 2014-09-25 01:25:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/601983002/1

[commit-bot: I haz the power, 2014-09-25 02:42:59]

Committed patchset #1 (id:1) as fcebab50f80e41df5524ef1cc7280f5604fd79a1

[commit-bot: I haz the power, 2014-09-25 02:43:39]

Patchset 1 (id:??) landed as
https://crrev.com/119c6fa8247481d2e36910d30175d0214fd2ece5
Cr-Commit-Position: refs/heads/master@{#296630}

[Lei Zhang, 2014-09-25 03:08:23]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/603833002/ by thestig@chromium.org.

The reason for reverting is: Broke Android bots:
http://build.chromium.org/p/chromium.linux/builders/Android%20Arm64%20Builder...
http://build.chromium.org/p/chromium.linux/builders/Android%20Builder%20%28db....