liblog: __android_log_is_loggable support Developer Options

- If logd.tag.<tag> is not found, check if persist.logd.tag.<tag> is available
- Do not turn off the isLoggable functionality on "user" builds

Bug: 19544788
Bug: 17760225
Change-Id: I3fec67b547aa431438965519507033798398e1e1
diff --git a/liblog/log_is_loggable.c b/liblog/log_is_loggable.c
index df67123..2e09192 100644
--- a/liblog/log_is_loggable.c
+++ b/liblog/log_is_loggable.c
@@ -28,7 +28,7 @@
         return def;
     }
     {
-        static const char log_namespace[] = "log.tag.";
+        static const char log_namespace[] = "persist.log.tag.";
         char key[sizeof(log_namespace) + strlen(tag)];
 
         strcpy(key, log_namespace);
@@ -37,6 +37,9 @@
         if (__system_property_get(key + 8, buf) <= 0) {
             buf[0] = '\0';
         }
+        if (!buf[0] && __system_property_get(key, buf) <= 0) {
+            buf[0] = '\0';
+        }
     }
     switch (toupper(buf[0])) {
         case 'V': return ANDROID_LOG_VERBOSE;
@@ -53,17 +56,6 @@
 
 int __android_log_is_loggable(int prio, const char *tag, int def)
 {
-    static char user;
-    int logLevel;
-
-    if (user == 0) {
-        char buf[PROP_VALUE_MAX];
-        if (__system_property_get("ro.build.type", buf) <= 0) {
-            buf[0] = '\0';
-        }
-        user = strcmp(buf, "user") ? -1 : 1;
-    }
-
-    logLevel = (user == 1) ? def : __android_log_level(tag, def);
+    int logLevel = __android_log_level(tag, def);
     return logLevel >= 0 && prio >= logLevel;
 }