Move signal_blocker to platform and use it by default in TEMP_FAILURE_RETRY.

runtime/bin/crypto_linux.cc

Index: runtime/bin/crypto_linux.cc
diff --git a/runtime/bin/crypto_linux.cc b/runtime/bin/crypto_linux.cc
index 849fe71a3f0f07e923c298a722886ad2d5624516..905bf77481a62744282c285f810c79d76f96eb43 100644
--- a/runtime/bin/crypto_linux.cc
+++ b/runtime/bin/crypto_linux.cc
@@ -10,6 +10,7 @@
 
 #include "bin/fdutils.h"
 #include "bin/crypto.h"
+#include "platform/signal_blocker.h"
 
 
 namespace dart {
@@ -18,8 +19,8 @@ namespace bin {
 bool Crypto::GetRandomBytes(intptr_t count, uint8_t* buffer) {
   intptr_t fd = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY));
   if (fd < 0) return false;
-  intptr_t bytes_read = read(fd, buffer, count);
-  close(fd);
+  intptr_t bytes_read = TEMP_FAILURE_RETRY(read(fd, buffer, count));
+  VOID_TEMP_FAILURE_RETRY(close(fd));
   return bytes_read == count;
 }