Enable SoftKeymasterDevice logging.

Bug: 20717652
Change-Id: I2397e5cd906d45515a0b2a5591705f458c1aceb0

keystore/keystore.cpp

@@ -43,8 +43,9 @@
 
 #include <hardware/keymaster0.h>
 
-#include <keymaster/softkeymaster.h>
 #include <keymaster/soft_keymaster_device.h>
+#include <keymaster/soft_keymaster_logger.h>
+#include <keymaster/softkeymaster.h>
 
 #include <UniquePtr.h>
 #include <utils/String8.h>
@@ -129,6 +130,10 @@ out:
     return rc;
 }
 
+// softkeymaster_logger appears not to be used in keystore, but it installs itself as the
+// logger used by SoftKeymasterDevice.
+static keymaster::SoftKeymasterLogger softkeymaster_logger;
+
 static int fallback_keymaster_device_initialize(keymaster1_device_t** dev) {
     keymaster::SoftKeymasterDevice* softkeymaster =
             new keymaster::SoftKeymasterDevice();