Use gettid directly in binder.

Bug: 17048545
Change-Id: I1df378135961e085a52f6cc5694ad74cd73aac19
diff --git a/IPCThreadState.cpp b/IPCThreadState.cpp
index 57c4638..ae8f648 100644
--- a/IPCThreadState.cpp
+++ b/IPCThreadState.cpp
@@ -682,7 +682,7 @@
 
 IPCThreadState::IPCThreadState()
     : mProcess(ProcessState::self()),
-      mMyThreadId(androidGetTid()),
+      mMyThreadId(gettid()),
       mStrictModePolicy(0),
       mLastTransactionBinderFlags(0)
 {