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This refactors the ProviderImpl in DeviceOrientation to make it more general.
This will make it easy to add other types of device data (such as DeviceMotion)
in the future and to have them use the same Provider/ProviderImpl.

This is an alternative to http://codereview.chromium.org/10689106.

TBR=avi
BUG=none
TEST=browser_tests:DeviceOrientationBrowserTest.BasicTest,
content_unittests --gtest_filter=DeviceOrientation*


Review URL: https://chromiumcodereview.appspot.com/10755002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@149864 0039d316-1c4b-4281-b951-d872f2087c98