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/source/thread_unittest.cc b/webrtc/system_wrappers/source/thread_unittest.cc
index a2228e6..99832d4 100644
--- a/webrtc/system_wrappers/source/thread_unittest.cc
+++ b/webrtc/system_wrappers/source/thread_unittest.cc
@@ -24,8 +24,7 @@
 
 TEST(ThreadTest, StartStop) {
   ThreadWrapper* thread = ThreadWrapper::CreateThread(&NullRunFunction, NULL);
-  unsigned int id = 42;
-  ASSERT_TRUE(thread->Start(id));
+  ASSERT_TRUE(thread->Start());
   EXPECT_TRUE(thread->Stop());
   delete thread;
 }
@@ -42,8 +41,7 @@
   bool flag = false;
   ThreadWrapper* thread = ThreadWrapper::CreateThread(&SetFlagRunFunction,
                                                       &flag);
-  unsigned int id = 42;
-  ASSERT_TRUE(thread->Start(id));
+  ASSERT_TRUE(thread->Start());
 
   // At this point, the flag may be either true or false.
   EXPECT_TRUE(thread->Stop());