Refactors TestSystemTrayDelegate into DefaultSystemTrayDelegate (2)

Original patch was reverted as TestSystemTrayDelegate had an ASH_EXPORT, which caused compile error win-aura builder.

DefaultSystemTrayDelegate is the no-op implementation and
TestSystemTrayDelegate contains the test related bits.

This also fixes a crash in the windows side as
TestSystemTrayDelegate::Shutdown() quits the message loop, which is
the wrong thing to do.

BUG=159693 284358
TEST=none
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Review URL: https://codereview.chromium.org/23792007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@223066 0039d316-1c4b-4281-b951-d872f2087c98
17 files changed