Revert "[vm, timeline] Fix compilation failed below macOS 10.14"

This reverts commit 156ef76.

Reason for revert: broke compilation on buildbots

Original change's description:
> [vm, timeline] Fix compilation failed below macOS 10.14
> 
> signpost.h exists in macOS 10.14 or above, so compilation failed below macOS 10.14
> 
> Change-Id: I97c4d6652f8330d3fc150186e41067c80c3b56f2
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/151101
> Commit-Queue: Vyacheslav Egorov <vegorov@google.com>
> Reviewed-by: Vyacheslav Egorov <vegorov@google.com>

TBR=vegorov@google.com,3630cn@sina.com

Change-Id: I04cd72a0c16a9e1d32d1735abf0fe42d35d240e1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/151380
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Commit-Queue: Vyacheslav Egorov <vegorov@google.com>

Author: mraleph

runtime/vm/timeline.cc

@@ -117,7 +117,9 @@ static TimelineEventRecorder* CreateTimelineRecorder() {
 #if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
       return new TimelineEventSystraceRecorder();
 #elif defined(HOST_OS_MACOS)
-      return new TimelineEventMacosRecorder();
+      if (__builtin_available(iOS 12.0, macOS 10.14, *)) {
+        return new TimelineEventMacosRecorder();
+      }
 #elif defined(HOST_OS_FUCHSIA)
       return new TimelineEventFuchsiaRecorder();
 #else
@@ -765,8 +767,10 @@ TimelineStream::TimelineStream(const char* name,
       enabled_(static_cast<uintptr_t>(enabled))
 #endif
 {
-#if defined(HOST_OS_SUPPORTS_SIGNPOST)
-  macos_log_ = os_log_create("Dart", name);
+#if defined(HOST_OS_MACOS)
+  if (__builtin_available(iOS 12.0, macOS 10.14, *)) {
+    macos_log_ = os_log_create("Dart", name);
+  }
 #endif
 }
 

runtime/vm/timeline.h

@@ -20,14 +20,8 @@
 #include <lib/trace-engine/instrumentation.h>
 #elif defined(HOST_OS_MACOS)
 #include <os/availability.h>
-#if defined(__MAC_10_14) || defined (__IPHONE_12_0)
-#define HOST_OS_SUPPORTS_SIGNPOST 1
-#endif
-//signpost.h exists in macOS 10.14, iOS 12 or above
-#if defined(HOST_OS_SUPPORTS_SIGNPOST)
 #include <os/signpost.h>
 #endif
-#endif
 
 namespace dart {
 
@@ -100,7 +94,7 @@ class TimelineStream {
 
 #if defined(HOST_OS_FUCHSIA)
   trace_site_t* trace_site() { return &trace_site_; }
-#elif defined(HOST_OS_SUPPORTS_SIGNPOST)
+#elif defined(HOST_OS_MACOS)
   os_log_t macos_log() { return macos_log_; }
 #endif
 
@@ -114,7 +108,7 @@ class TimelineStream {
 
 #if defined(HOST_OS_FUCHSIA)
   trace_site_t trace_site_ = {};
-#elif defined(HOST_OS_SUPPORTS_SIGNPOST)
+#elif defined(HOST_OS_MACOS)
   os_log_t macos_log_ = {};
 #endif
 };

runtime/vm/timeline_macos.cc

@@ -5,14 +5,11 @@
 #include "vm/globals.h"
 #if defined(HOST_OS_MACOS) && defined(SUPPORT_TIMELINE)
 
+#include <os/signpost.h>
 
 #include "vm/log.h"
 #include "vm/timeline.h"
 
-#if defined(HOST_OS_SUPPORTS_SIGNPOST)
-#include <os/signpost.h>
-#endif
-
 namespace dart {
 
 // Only available on iOS 12.0, macOS 10.14 or above
@@ -26,7 +23,6 @@ void TimelineEventMacosRecorder::OnEvent(TimelineEvent* event) {
     return;
   }
 
-#if defined(HOST_OS_SUPPORTS_SIGNPOST)
   os_log_t log = event->stream_->macos_log();
   if (!os_signpost_enabled(log)) {
     return;
@@ -79,7 +75,6 @@ void TimelineEventMacosRecorder::OnEvent(TimelineEvent* event) {
     default:
       break;
   }
-#endif  // defined(HOST_OS_SUPPORTS_SIGNPOST)
 }
 
 }  // namespace dart