Created new Task.h file to contain task classes.

Test: tested Reboot {target} + Flash {partition} on raven device
Bug: 194686221
Change-Id: I0d80230d682f80af12cca9705df0172651bf4461
diff --git a/fastboot/fastboot.h b/fastboot/fastboot.h
index c23793a..d7ad5df 100644
--- a/fastboot/fastboot.h
+++ b/fastboot/fastboot.h
@@ -25,6 +25,7 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
+#pragma once
 
 #include <bootimg.h>