Move FilePathWatcher class from chrome/browser/... to content/common...

The service process needs FilePathWatcher, and with this change I
got rid of the dependency on BrowserThread which allows it to be moved to common/...
I also tried my hand at a kqueue impl on the Mac, but failed.
See http://code.google.com/p/chromium/issues/detail?id=54822#c13 for details.

BUG=74983
TEST=BUILD

Review URL: http://codereview.chromium.org/6670081

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@78664 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/content/browser/plugin_service.h b/content/browser/plugin_service.h
index e142a903..46e34a6 100644
--- a/content/browser/plugin_service.h
+++ b/content/browser/plugin_service.h
@@ -33,7 +33,7 @@
 #endif
 
 #if defined(OS_LINUX)
-#include "chrome/browser/file_path_watcher/file_path_watcher.h"
+#include "content/common/file_path_watcher/file_path_watcher.h"
 #endif
 
 #if defined(OS_CHROMEOS)