liblog: log_time add explicit to some constructors.

Add explicit to constructors, to prevent implicit conversions.

Test: compile
Bug: 37378309
Change-Id: I3f9f8d561e84c492eafa6528db7c238da072dad8
diff --git a/liblog/include/log/log_time.h b/liblog/include/log/log_time.h
index 5f70f7d..9ece0b3 100644
--- a/liblog/include/log/log_time.h
+++ b/liblog/include/log/log_time.h
@@ -41,13 +41,12 @@
   static const uint32_t tv_sec_max = 0xFFFFFFFFUL;
   static const uint32_t tv_nsec_max = 999999999UL;
 
-  log_time(const timespec& T) {
-    tv_sec = static_cast<uint32_t>(T.tv_sec);
-    tv_nsec = static_cast<uint32_t>(T.tv_nsec);
+  log_time(const timespec& T)
+      : tv_sec(static_cast<uint32_t>(T.tv_sec)),
+        tv_nsec(static_cast<uint32_t>(T.tv_nsec)) {
   }
-  log_time(uint32_t sec, uint32_t nsec) {
-    tv_sec = sec;
-    tv_nsec = nsec;
+  explicit log_time(uint32_t sec, uint32_t nsec = 0)
+      : tv_sec(sec), tv_nsec(nsec) {
   }
 #ifdef _SYSTEM_CORE_INCLUDE_PRIVATE_ANDROID_LOGGER_H_
 #define __struct_log_time_private_defined
@@ -56,14 +55,14 @@
   log_time() {
   }
 #ifdef __linux__
-  log_time(clockid_t id) {
+  explicit log_time(clockid_t id) {
     timespec T;
     clock_gettime(id, &T);
     tv_sec = static_cast<uint32_t>(T.tv_sec);
     tv_nsec = static_cast<uint32_t>(T.tv_nsec);
   }
 #endif
-  log_time(const char* T) {
+  explicit log_time(const char* T) {
     const uint8_t* c = reinterpret_cast<const uint8_t*>(T);
     tv_sec = c[0] | (static_cast<uint32_t>(c[1]) << 8) |
              (static_cast<uint32_t>(c[2]) << 16) |