Added support for Delete Task

Test: tested delete-logical-partition {partition} and flashall on Raven

Change-Id: I04f07c8132159deda42434b9178e8c98d5ab768b
Bug: 194686221
diff --git a/fastboot/task.h b/fastboot/task.h
index 7aa19a3..b90fcd1 100644
--- a/fastboot/task.h
+++ b/fastboot/task.h
@@ -92,3 +92,13 @@
     const std::string size_;
     const std::string slot_;
 };
+
+class DeleteTask : public Task {
+  public:
+    DeleteTask(FlashingPlan* _fp, const std::string& _pname);
+    void Run() override;
+
+  private:
+    FlashingPlan* fp_;
+    const std::string pname_;
+};