Fix crash in a few of the tests in content_browsertests on Linux. The problem was that DesktopActiv…

base/scoped_observer.h

Index: base/scoped_observer.h
===================================================================
--- base/scoped_observer.h	(revision 159993)
+++ base/scoped_observer.h	(working copy)
@@ -35,6 +35,14 @@
     source->RemoveObserver(observer_);
   }
 
+  bool IsObserving(Source* source) const {
+    for (size_t i = 0; i < sources_.size(); ++i) {
+      if (sources_[i] == source)
+        return true;
+    }
+    return false;
+  }
+
  private:
   Observer* observer_;