Improve error handling in the process library.

runtime/bin/socket_macos.cc

Index: runtime/bin/socket_macos.cc
diff --git a/runtime/bin/socket_macos.cc b/runtime/bin/socket_macos.cc
index 231bcccb93cfa0dfb3c7e22f565d924e62ecd36d..e5472379d25ff9d5fee6011836e412bc24bcf336 100644
--- a/runtime/bin/socket_macos.cc
+++ b/runtime/bin/socket_macos.cc
@@ -63,20 +63,20 @@ intptr_t Socket::Available(intptr_t fd) {
 intptr_t Socket::Read(intptr_t fd,
                       void* buffer,
                       intptr_t num_bytes) {
-  assert(fd >= 0);
+  ASSERT(fd >= 0);
   intptr_t read_bytes = read(fd, buffer, num_bytes);
   return read_bytes;
 }
 
 
 intptr_t Socket::Write(intptr_t fd, const void* buffer, intptr_t num_bytes) {
-  assert(fd >= 0);
+  ASSERT(fd >= 0);
   return write(fd, buffer, num_bytes);
 }
 
 
 intptr_t Socket::GetPort(intptr_t fd) {
-  assert(fd >= 0);
+  ASSERT(fd >= 0);
   struct sockaddr_in socket_address;
   socklen_t size = sizeof(socket_address);
   if (getsockname(fd, reinterpret_cast<struct sockaddr *>(&socket_address),