don't try to call BalloonViewHost on non-cros

don't try to call BalloonViewHost on non-cros

Avoids link error:

[14->2/16 ~0] LINK(DLL) initial\chrome.dll
FAILED: python gyp-win-tool link-wrapper "c:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin\link.exe" /nologo /IMPLIB:initial\chrome.dll.lib /DLL /OUT:initial\chrome.dll /PDB:initial\chrome.dll.pdb @initial\chrome.dll.rsp
browser.balloon_collection_impl_ash.obj : error LNK2019: unresolved external symbol "public: bool __thiscall chromeos::BalloonViewHost::AddWebUIMessageCallback(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &,class base::Callback<void __cdecl(class base::ListValue const *)> const &)" (?AddWebUIMessageCallback@BalloonViewHost@chromeos@@QAE_NABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@ABV?$Callback@$$A6AXPBVListValue@base@@@Z@base@@@Z) referenced in function
"public: bool __thiscall BalloonCollectionImplAsh::AddWebUIMessageCallback(class Notification const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &,class base::Callback<void __cdecl(class base::ListValue const *)>
const &)" (?AddWebUIMessageCallback@BalloonCollectionImplAsh@@QAE_NABVNotification@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@ABV?$Callback@$$A6AXPBVListValue@base@@@Z@base@@@Z)
initial\chrome.dll : fatal error LNK1120: 1 unresolved externals


R=ben@chromium.org,cpu@chromium.org


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=141789

[scottmg, 2012-06-12 21:46:36]

I have no idea if this is the correct fix, but alternatively we need something
else for use_aura=1.

[Ben Goodger (Google), 2012-06-12 22:17:15]

lgtm

[commit-bot: I haz the power, 2012-06-12 22:18:54]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/scottmg@chromium.org/10540128/1

[commit-bot: I haz the power, 2012-06-12 23:41:21]

Change committed as 141789