Unify Sampler implementation across platforms using signals to suspend thread

src/log.h

Index: src/log.h
diff --git a/src/log.h b/src/log.h
index 29bc8e81ffa6d969496ce26183e066ed40a3bdf5..21f387e91b41a0939b15477a92b40a663ea72a7a 100644
--- a/src/log.h
+++ b/src/log.h
@@ -74,6 +74,7 @@ namespace internal {
 class LogMessageBuilder;
 class Profiler;
 class Semaphore;
+struct TickSample;
 class Ticker;
 class Isolate;
 class PositionsRecorder;