AU: Try delta updates first, then full updates

src/platform/update_engine/action_processor.h

Index: src/platform/update_engine/action_processor.h
diff --git a/src/platform/update_engine/action_processor.h b/src/platform/update_engine/action_processor.h
index 938a81d0f7233055e5b87fc9b8d28c49b42e155f..8311b8a633f4eade92f903448095f6f93ac3dbea 100644
--- a/src/platform/update_engine/action_processor.h
+++ b/src/platform/update_engine/action_processor.h
@@ -78,8 +78,9 @@ class ActionProcessor {
 class ActionProcessorDelegate {
  public:
   // Called when all processing in an ActionProcessor has completed. A pointer
-  // to the ActionProcessor is passed.
-  virtual void ProcessingDone(const ActionProcessor* processor) {}
+  // to the ActionProcessor is passed. success is true iff all actions
+  // completed successfully
+  virtual void ProcessingDone(const ActionProcessor* processor, bool success) {}
 
   // Called when processing has stopped. Does not mean that all Actions have
   // completed. If/when all Actions complete, ProcessingDone() will be called.