Remove thread id from ThreadWrapper::Start().

Removes ThreadPosix::InitParams and a corresponding wait for an event.
This unblocks ThreadPosix::Start which had to wait for thread scheduling
for an event to trigger on the spawned thread, giving faster Start()
calls.

BUG=4413
R=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/43699004

Cr-Commit-Position: refs/heads/master@{#8709}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8709 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/system_wrappers/interface/thread_wrapper.h b/webrtc/system_wrappers/interface/thread_wrapper.h
index 53a2c0a..af1405d 100644
--- a/webrtc/system_wrappers/interface/thread_wrapper.h
+++ b/webrtc/system_wrappers/interface/thread_wrapper.h
@@ -73,8 +73,7 @@
   // Additionally, it tries to set thread priority according to the priority
   // from when CreateThread was called. However, failure to set priority will
   // not result in a false return value.
-  // TODO(tommi): Remove the id parameter.
-  virtual bool Start(unsigned int& id) = 0;
+  virtual bool Start() = 0;
 
   // Stops the spawned thread and waits for it to be reclaimed with a timeout
   // of two seconds. Will return false if the thread was not reclaimed.