Change ActiveTabTest to do setup in SetUp rather than its constructor.

chrome/browser/extensions/active_tab_unittest.cc

Index: chrome/browser/extensions/active_tab_unittest.cc
diff --git a/chrome/browser/extensions/active_tab_unittest.cc b/chrome/browser/extensions/active_tab_unittest.cc
index c1c00e9b9230aaaf762a103cf983d215a65a7a8b..7db3c85f925b8695edfdc32a3e02f9c309b18fad 100644
--- a/chrome/browser/extensions/active_tab_unittest.cc
+++ b/chrome/browser/extensions/active_tab_unittest.cc
@@ -64,6 +64,10 @@ class ActiveTabTest : public TabContentsTestHarness {
         extension_without_active_tab(
             CreateTestExtension("without activeTab", false)),
         ui_thread_(BrowserThread::UI, MessageLoop::current()) {
+  }
+
+  virtual void SetUp() {
+    TabContentsTestHarness::SetUp();
     Feature::SetChannelForTesting(chrome::VersionInfo::CHANNEL_UNKNOWN);
   }