- Add a SetPriority method to ThreadWrapper

- Remove 'priority' from CreateThread and related member variables from implementations
- Make supplying a name for threads, non-optional

BUG=
R=magjed@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/44729004

Cr-Commit-Position: refs/heads/master@{#8810}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8810 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/system_wrappers/source/condition_variable_unittest.cc

@@ -145,7 +145,7 @@ class CondVarTest : public ::testing::Test {
 
   virtual void SetUp() {
     thread_ = ThreadWrapper::CreateThread(&WaitingRunFunction,
-                                          &baton_);
+                                          &baton_, "CondVarTest");
     ASSERT_TRUE(thread_->Start());
   }