Add Directory.systemTemp getter to replace createSystemTemp().

runtime/bin/directory_macos.cc

Index: runtime/bin/directory_macos.cc
diff --git a/runtime/bin/directory_macos.cc b/runtime/bin/directory_macos.cc
index 5757a9c1a05075795acf968827ede4c2c4fa463d..e046bb5683f33db3bdbeb8d9d692c69275cae8d1 100644
--- a/runtime/bin/directory_macos.cc
+++ b/runtime/bin/directory_macos.cc
@@ -361,27 +361,25 @@ bool Directory::Create(const char* dir_name) {
 }
 
 
-char* Directory::CreateTemp(const char* const_template, bool system) {
-  // Returns a new, unused directory name, modifying the contents of
-  // dir_template.  Creates the directory with the permissions specified
+char* Directory::SystemTemp() {
+  const char* temp_dir = getenv("TMPDIR");
+  if (temp_dir == NULL) {
+    temp_dir = getenv("TMP");
+  }
+  if (temp_dir == NULL) {
+    temp_dir = "/tmp";
+  }
+  return strdup(temp_dir);
+}
+
+
+char* Directory::CreateTemp(const char* prefix) {
+  // Returns a new, unused directory name, adding characters to the end
+  // of prefix.  Creates the directory with the permissions specified
   // by the process umask.
   // The return value must be freed by the caller.
   PathBuffer path;
-  if (system) {
-    const char* temp_dir = getenv("TMPDIR");
-    if (temp_dir == NULL) {
-      temp_dir = getenv("TMP");
-    }
-    if (temp_dir != NULL) {
-      path.Add(temp_dir);
-      if (temp_dir[strlen(temp_dir) - 1] != '/') {
-        path.Add("/");
-      }
-    } else {
-      path.Add("/tmp/");
-    }
-  }
-  path.Add(const_template);
+  path.Add(prefix);
   if (!path.Add("XXXXXX")) {
     // Pattern has overflowed.
     return NULL;
@@ -393,11 +391,7 @@ char* Directory::CreateTemp(const char* const_template, bool system) {
   if (result == NULL) {
     return NULL;
   }
-  int length = strlen(path.AsString());
-  result = static_cast<char*>(malloc(length + 1));
-  strncpy(result, path.AsString(), length);
-  result[length] = '\0';
-  return result;
+  return strdup(result);
 }