Use getenv to get TMPDIR path on macOS as well

This avoids the dependency on bundles or frameworks and it's the
solution used by other tools such as Ninja and even C++ standard
library.

Change-Id: I423a8919ee67b6734e090a783122fb094481724e
Reviewed-on: https://gn-review.googlesource.com/c/2941
Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Petr Hosek <phosek@google.com>

base/files/file_util_posix.cc

diff --git a/base/files/file_util_posix.cc b/base/files/file_util_posix.cc
index 23c7cb4..2ef6afc 100644
--- a/base/files/file_util_posix.cc
+++ b/base/files/file_util_posix.cc
@@ -111,15 +111,7 @@
 }
 
 std::string TempFileName() {
-#if defined(OS_MACOSX)
-  return StringPrintf(".%s.XXXXXX", base::mac::BaseBundleID());
-#endif
-
-#if defined(GOOGLE_CHROME_BUILD)
-  return std::string(".com.google.Chrome.XXXXXX");
-#else
   return std::string(".org.chromium.Chromium.XXXXXX");
-#endif
 }
 
 #if defined(OS_LINUX) || defined(OS_AIX)
@@ -578,8 +570,6 @@
 
 #endif  // !OS_FUCHSIA
 
-#if !defined(OS_MACOSX)
-// This is implemented in file_util_mac.mm for Mac.
 bool GetTempDir(FilePath* path) {
   const char* tmp = getenv("TMPDIR");
   if (tmp) {
@@ -590,7 +580,6 @@
   *path = FilePath("/tmp");
   return true;
 }
-#endif  // !defined(OS_MACOSX)
 
 #if !defined(OS_MACOSX)  // Mac implementation is in file_util_mac.mm.
 FilePath GetHomeDir() {