Do not rely on uniquiness of pthread_t

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index c2b2df83625cf26814564b1f0ca1be65f8f447f0..a2373cdd14924507bf33ef34e08e994a2a826588 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -4625,7 +4625,7 @@ int V8::GetLogLines(int from_pos, char* dest_buf, int max_size) {
 int V8::GetCurrentThreadId() {
   i::Isolate* isolate = i::Isolate::Current();
   EnsureInitializedForIsolate(isolate, "V8::GetCurrentThreadId()");
-  return isolate->thread_id();
+  return isolate->thread_id().ToInteger();
 }
 
 
@@ -4636,10 +4636,11 @@ void V8::TerminateExecution(int thread_id) {
   // If the thread_id identifies the current thread just terminate
   // execution right away.  Otherwise, ask the thread manager to
   // terminate the thread with the given id if any.
-  if (thread_id == isolate->thread_id()) {
+  i::ThreadId internal_tid = i::ThreadId::FromInteger(thread_id);
+  if (isolate->thread_id().Equals(internal_tid)) {
     isolate->stack_guard()->TerminateExecution();
   } else {
-    isolate->thread_manager()->TerminateExecution(thread_id);
+    isolate->thread_manager()->TerminateExecution(internal_tid);
   }
 }