Revert "Re-land: Use os_log instead of syslog on Apple platforms (#16549)" (#16558)

This reverts commit 6aacf5e7.

fml/logging.cc

@@ -11,8 +11,7 @@
 
 #if defined(OS_ANDROID)
 #include <android/log.h>
-#elif defined(OS_MACOSX)
-#include <os/log.h>
+#elif defined(OS_IOS)
 #include <syslog.h>
 #endif
 
@@ -82,37 +81,8 @@ LogMessage::~LogMessage() {
       break;
   }
   __android_log_write(priority, "flutter", stream_.str().c_str());
-#elif defined(OS_MACOSX)
-  const char* chars = stream_.str().c_str();
-  // Unified logging (os_log) became available in iOS 9.0 and syslog stopped
-  // working in iOS 13.0. idevicesyslog made device syslog available on the
-  // connected host, but there is no known API to view device unified logging on
-  // the host. Flutter tool will continue to observe syslog on devices older
-  // than iOS 13.0 since it provides more logging context, particularly for
-  // application crashes.
-  if (__builtin_available(iOS 13.0, macOS 10.11, *)) {
-    os_log_t engine_log = os_log_create("io.flutter", "engine");
-    switch (severity_) {
-      // TODO(flutter/flutter#45931): LogSeverity LOG_INFO and LOG_WARNING
-      // collide with syslog log level macros.
-      case 0 /* LOG_INFO */:
-        os_log_debug(engine_log, "%s", chars);
-        break;
-      case 1 /* LOG_WARNING */:
-      case LOG_ERROR:
-        os_log_error(engine_log, "%s", chars);
-        break;
-      case LOG_FATAL:
-        os_log_fault(engine_log, "%s", chars);
-        break;
-      default:
-        os_log(engine_log, "%s", chars);
-        break;
-    }
-  } else {
-    syslog(LOG_ALERT, "%s", chars);
-  }
-
+#elif defined(OS_IOS)
+  syslog(LOG_ALERT, "%s", stream_.str().c_str());
 #else
   std::cerr << stream_.str();
   std::cerr.flush();

lib/ui/dart_runtime_hooks.cc

@@ -30,8 +30,7 @@
 
 #if defined(OS_ANDROID)
 #include <android/log.h>
-#elif defined(OS_MACOSX)
-#include <os/log.h>
+#elif defined(OS_IOS)
 extern "C" {
 // Cannot import the syslog.h header directly because of macro collision.
 extern void syslog(int, const char*, ...);
@@ -200,29 +199,19 @@ void Logger_PrintString(Dart_NativeArguments args) {
     // Write to the logcat on Android.
     __android_log_print(ANDROID_LOG_INFO, logger_prefix.c_str(), "%.*s",
                         (int)length, chars);
-#elif defined(OS_MACOSX)
+#elif defined(OS_IOS)
+    // Write to syslog on iOS.
+    //
     // TODO(cbracken): replace with dedicated communication channel and bypass
     // iOS logging APIs altogether.
-    //
-    // Unified logging (os_log) became available in iOS 9.0 and syslog stopped
-    // working in iOS 13.0. idevicesyslog made device syslog available on the
-    // connected host, but there is no known API to view device unified logging
-    // on the host. Flutter tool will continue to observe syslog on devices
-    // older than iOS 13.0 since it provides more logging context, particularly
-    // for application crashes.
-    if (__builtin_available(iOS 13.0, macOS 10.11, *)) {
-      os_log_t dart_log = os_log_create("io.flutter", "dart");
-      os_log(dart_log, "%.*s", static_cast<int>(length), chars);
-    } else {
-      syslog(1 /* LOG_ALERT */, "%.*s", static_cast<int>(length), chars);
-    }
+    syslog(1 /* LOG_ALERT */, "%.*s", (int)length, chars);
 #else
     std::cout << log_string << std::endl;
 #endif
   }
 
   if (dart::bin::ShouldCaptureStdout()) {
-    // Report print output on the Stdout stream.
+    // For now we report print output on the Stdout stream.
     uint8_t newline[] = {'\n'};
     Dart_ServiceSendDataEvent("Stdout", "WriteEvent",
                               reinterpret_cast<const uint8_t*>(chars), length);