Add a hardware_class attribute (for HWID, HWQual ID) to the Omaha request.

BUG=1600
TEST=unit tests, gmerge and looked at request logs

Review URL: http://codereview.chromium.org/3007020
diff --git a/action.h b/action.h
index 9e6eb94..7ce9f60 100644
--- a/action.h
+++ b/action.h
@@ -125,9 +125,7 @@
 template<typename SubClass>
 class Action : public AbstractAction {
  public:
-  virtual ~Action() {
-    LOG(INFO) << "Action died";
-  }
+  virtual ~Action() {}
 
   // Attaches an input pipe to this Action. This is optional; an Action
   // doesn't need to have an input pipe. The input pipe must be of the type