Delete SignalThread class.

webrtc/rtc_base/messagequeue.cc

Index: webrtc/rtc_base/messagequeue.cc
diff --git a/webrtc/rtc_base/messagequeue.cc b/webrtc/rtc_base/messagequeue.cc
index cafb70bd002faaf3241db5f9f4633b70767cb887..fce1906a41e0d5c5db6c07e0c5c4bd07ccf30cf8 100644
--- a/webrtc/rtc_base/messagequeue.cc
+++ b/webrtc/rtc_base/messagequeue.cc
@@ -44,6 +44,16 @@ class SCOPED_LOCKABLE DebugNonReentrantCritScope {
 
   RTC_DISALLOW_COPY_AND_ASSIGN(DebugNonReentrantCritScope);
 };
+
+class FunctorPostMessageHandler : public MessageHandler {
+ public:
+  void OnMessage(Message* msg) override {
+    RunnableData* data = static_cast<RunnableData*>(msg->pdata);
+    data->Run();
+    delete data;
+  }
+};
+
 }  // namespace
 
 //------------------------------------------------------------------
@@ -529,4 +539,12 @@ void MessageQueue::Dispatch(Message *pmsg) {
   }
 }
 
+void MessageQueue::PostFunctorInternal(const Location& posted_from,
+                                       RunnableData* message_data) {
+  // Use static to ensure it outlives this scope. Safe since
+  // FunctorPostMessageHandler keeps no state.
+  static FunctorPostMessageHandler handler;
+  Post(posted_from, &handler, 0, message_data);
+}
+
 }  // namespace rtc