Add LOG_SILENT LogPriority

(This is a merge of http://go/wvgerrit/73743)

The CE CDM implements the ability to silence all logging with a "silent"
log level. However, under the covers, this assigned a value to g_cutoff
that was not a member of LogPriority, which fails some extremely strict
checks. This patch just adds a matching entry to LogPriority so that
"silent" is now a valid level in that enum.

Bug: 118622359
Test: CE CDM Build
Test: Android Build
Change-Id: Idafb26b7c5f9a24a32c84da9b3c5595434ef07fe

libwvdrmengine/cdm/util/include/log.h

@@ -14,11 +14,15 @@ namespace wvcdm {
 // Simple logging class. The implementation is platform dependent.
 
 typedef enum {
-  LOG_ERROR,
-  LOG_WARN,
-  LOG_INFO,
-  LOG_DEBUG,
-  LOG_VERBOSE
+  // This log level should only be used for |g_cutoff|, in order to silence all
+  // logging. It should never be passed to |Log()| as a log level.
+  LOG_SILENT = -1,
+
+  LOG_ERROR = 0,
+  LOG_WARN = 1,
+  LOG_INFO = 2,
+  LOG_DEBUG = 3,
+  LOG_VERBOSE = 4,
 } LogPriority;
 
 extern LogPriority g_cutoff;