Add PSKKeyManager to enable the use of TLS-PSK.

TLS-PSK is supported by the underlying TLS/SSL stack (based on
Conscrypt). This CL simply exposes this support in the Android
framework.

TLS-PSK is a set of TLS/SSL cipher suites which rely on a symmetric
pre-shared key (PSK) to secure the TLS/SSL connection and mutually
authenticate its peers. These cipher suites may be a more natural fit
compared to conventional public key based cipher suites in some
scenarios where communication between peers is bootstrapped via a
separate step (for example, a pairing step) and requires both peers
to authenticate each other. In such scenarios a symmetric key (PSK)
can be exchanged during the bootstrapping step, removing the need to
generate and exchange public key pairs and X.509 certificates.

Bug: 15073623
Change-Id: Idf2a773db3021de3d2ad144c5cc63d2415eb8e91
diff --git a/Android.mk b/Android.mk
index 4875cc5..ada9173 100644
--- a/Android.mk
+++ b/Android.mk
@@ -605,8 +605,12 @@
 framework_docs_LOCAL_DROIDDOC_HTML_DIR := docs/html
 # The since flag (-since N.xml API_LEVEL) is used to add API Level information
 # to the reference documentation. Must be in order of oldest to newest.
+#
+# Conscrypt (com.android.org.conscrypt) is an implementation detail and should
+# not be referenced in the documentation.
 framework_docs_LOCAL_DROIDDOC_OPTIONS := \
     -knowntags ./frameworks/base/docs/knowntags.txt \
+    -hidePackage com.android.org.conscrypt \
     -since $(SRC_API_DIR)/1.xml 1 \
     -since $(SRC_API_DIR)/2.xml 2 \
     -since $(SRC_API_DIR)/3.xml 3 \