Update thread annotiation macros in rtc_base to use RTC_ prefix

webrtc/rtc_base/thread_unittest.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 318 matching lines @@
       value_ = value;
     }
 
     bool Get() {
       CritScope lock(&crit_);
       return value_;
     }
 
    private:
     CriticalSection crit_;
-    bool value_ GUARDED_BY(crit_);
+    bool value_ RTC_GUARDED_BY(crit_);
   };
 
   struct LocalFuncs {
     static void Set(LockedBool* out) { out->Set(true); }
     static void InvokeSet(Thread* thread, LockedBool* out) {
       thread->Invoke<void>(RTC_FROM_HERE, Bind(&Set, out));
     }
 
     // Set |out| true and call InvokeSet on |thread|.
     static void SetAndInvokeSet(LockedBool* out,
@@ skipping 286 matching lines @@
   // Execute pending calls with id == 5.
   EXPECT_TRUE(invoker.Flush(5));
   EXPECT_TRUE(flag1.get());
   EXPECT_FALSE(flag2.get());
   flag1 = false;
   // Execute all pending calls. The id == 5 call should not execute again.
   EXPECT_TRUE(invoker.Flush());
   EXPECT_FALSE(flag1.get());
   EXPECT_TRUE(flag2.get());
 }