releasetools: ota_from_target_files: add FullOTA_PostValidate

Change-Id: I152412049f90fd546d4516cc064238c3192be553
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 7196c48..982e398 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -1013,6 +1013,11 @@
     used to install the image for the device's baseband processor."""
     return self._DoCall("FullOTA_InstallEnd")
 
+  def FullOTA_PostValidate(self):
+    """Called after installing and validating /system; typically this is
+    used to resize the system partition after a block based installation."""
+    return self._DoCall("FullOTA_PostValidate")
+
   def IncrementalOTA_Assertions(self):
     """Called after emitting the block of assertions at the top of an
     incremental OTA package.  Implementations can add whatever