Reduce the space used by the stack for the profiling thread.

src/platform-macos.cc

Index: src/platform-macos.cc
===================================================================
--- src/platform-macos.cc	(revision 10489)
+++ src/platform-macos.cc	(working copy)
@@ -473,20 +473,14 @@
   pthread_t thread_;  // Thread handle for pthread.
 };
 
+
 Thread::Thread(const Options& options)
     : data_(new PlatformData),
-      stack_size_(options.stack_size) {
-  set_name(options.name);
+      stack_size_(options.stack_size()) {
+  set_name(options.name());
 }
 
 
-Thread::Thread(const char* name)
-    : data_(new PlatformData),
-      stack_size_(0) {
-  set_name(name);
-}
-
-
 Thread::~Thread() {
   delete data_;
 }
@@ -736,10 +730,13 @@
   thread_act_t profiled_thread_;
 };
 
+
 class SamplerThread : public Thread {
  public:
+  static const int kSamplerThreadStackSize = 32 * KB;
+
   explicit SamplerThread(int interval)
-      : Thread("SamplerThread"),
+      : Thread(Thread::Options("SamplerThread", kSamplerThreadStackSize)),
         interval_(interval) {}
 
   static void AddActiveSampler(Sampler* sampler) {