content: Fix a typo in GN common/BUILD.gn file.

content: Fix a typo in GN common/BUILD.gn file.

I got this by change when I ran:
$ gn gen out/Debug_gn --args='os="linux" cpu_arch="arm"'
ERROR at //content/common/BUILD.gn:151:31: Undefined identifier
    if (cpu_arch != "arm" || !is_chromos) {
                             ^---------

BUG=None
TEST=above
TBR=brettw@chromium.org
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272685

[tfarina, 2014-05-24 02:16:40]

TBRing...

Scott, fyi.

[tfarina, 2014-05-24 02:22:53]

The CQ bit was checked by tfarina@chromium.org

[commit-bot: I haz the power, 2014-05-24 02:23:45]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tfarina@chromium.org/302443002/1

[brettw, 2014-05-24 02:24:14]

lgtm

[commit-bot: I haz the power, 2014-05-24 02:28:01]

Change committed as 272685