Fixes metrics collection during CdmEngine close.

This fixes a problem where a CdmEngine instance (and its sessions) could
be closed before its metrics could be collected. The change allows the
wv_content_decryption_module to extract metrics from instances about to
be closed. These are held until reported to the caller.

Test: Manually verified that collection is now occurring correctly. Also
added unit test: wv_cdm_metric_test.

This is a merge from wvgerrit/29069

Change-Id: If82bfd5cae3b72b9d14ab4741424a7ae7cc0a3a6

libwvdrmengine/mediacrypto/Android.mk

@@ -22,6 +22,7 @@ LOCAL_HEADER_LIBRARIES := \
   libutils_headers
 
 LOCAL_STATIC_LIBRARIES := \
+  libcdm_protos \
   libcrypto_static \
 
 LOCAL_SHARED_LIBRARIES := \
@@ -58,6 +59,7 @@ LOCAL_HEADER_LIBRARIES := \
   libutils_headers
 
 LOCAL_STATIC_LIBRARIES := \
+  libcdm_protos \
   libcrypto_static \
   libwidevinehidl_utils \