Update Security String to 2016-05-01 in preparation for May 2016 Security OTA

b/27724973

Change-Id: I572123586730e45b304f352c8b0fd6371ff5788b
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 8cc6900..c91315e 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -68,21 +68,20 @@
   PLATFORM_VERSION_ALL_CODENAMES := $(PLATFORM_VERSION_CODENAME)
 endif
 
-ifeq "REL" "$(PLATFORM_VERSION_CODENAME)"
-  PLATFORM_PREVIEW_SDK_VERSION := 0
-else
-  ifeq "" "$(PLATFORM_PREVIEW_SDK_VERSION)"
-    # This is the definition of a preview SDK version over and above the current
-    # platform SDK version. Unlike the platform SDK version, a higher value
-    # for preview SDK version does NOT mean that all prior preview APIs are
-    # included. Packages reading this value to determine compatibility with
-    # known APIs should check that this value is precisely equal to the preview
-    # SDK version the package was built for, otherwise it should fall back to
-    # assuming the device can only support APIs as of the previous official
-    # public release.
-    # This value will always be 0 for release builds.
-    PLATFORM_PREVIEW_SDK_VERSION := 0
-  endif
+ifeq "" "$(PLATFORM_SECURITY_PATCH)"
+  # Used to indicate the security patch that has been applied to the device.
+  # Can be an arbitrary string, but must be a single word.
+  #
+  # If there is no $PLATFORM_SECURITY_PATCH set, keep it empty.
+  PLATFORM_SECURITY_PATCH := 2016-05-01
+endif
+
+ifeq "" "$(PLATFORM_BASE_OS)"
+  # Used to indicate the base os applied to the device.
+  # Can be an arbitrary string, but must be a single word.
+  #
+  # If there is no $PLATFORM_BASE_OS set, keep it empty.
+  PLATFORM_BASE_OS :=
 endif
 
 ifeq "" "$(DEFAULT_APP_TARGET_SDK)"