Add BASE_API to SystemMonitor::PowerObserver to be able to export net::HttpNetworkLayer
Add BASE_API to SystemMonitor::PowerObserver to be able to
export net::HttpNetworkLayer

BUG=76997
TEST=NONE
Review URL: http://codereview.chromium.org/6992032

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@86492 0039d316-1c4b-4281-b951-d872f2087c98

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