Introduce UsageTableHeader class

[ Merge of http://go/wvgerrit/23820 ]

The UsageTableHeader class is a singleton that CDM sessions will share.
A separate object will be created for each security level. The class
synchronizes access to usage table header and associated data-structures
and controls when they are read in or written out to non-secure persistent
storage. Upgrades from a fixed size usage table (supported by previous
versions of the OEMCrypto API v9-12) are handled by this class.

b/34327459

Test: Verified by unit/integration tests on angler

Change-Id: Ifc5996985e76bc260c01e55bc12aab1248389a80

libwvdrmengine/cdm/Android.mk

@@ -35,6 +35,7 @@ LOCAL_SRC_FILES := \
     $(CORE_SRC_DIR)/policy_engine.cpp \
     $(CORE_SRC_DIR)/privacy_crypto_openssl.cpp \
     $(CORE_SRC_DIR)/service_certificate.cpp \
+    $(CORE_SRC_DIR)/usage_table_header.cpp \
     $(SRC_DIR)/ami_adapter.cpp \
     $(SRC_DIR)/wv_content_decryption_module.cpp \
     $(METRICS_SRC_DIR)/distribution.cpp \