Update clang to r339409.

Change-Id: I800772d2d838223be1f6b40d490c4591b937fca2
diff --git a/linux-x64/clang/include/llvm/Analysis/CaptureTracking.h b/linux-x64/clang/include/llvm/Analysis/CaptureTracking.h
index 8d2c095..7a869a5 100644
--- a/linux-x64/clang/include/llvm/Analysis/CaptureTracking.h
+++ b/linux-x64/clang/include/llvm/Analysis/CaptureTracking.h
@@ -46,7 +46,7 @@
   /// to speed up capture-tracker queries.
   bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures,
                                   bool StoreCaptures, const Instruction *I,
-                                  DominatorTree *DT, bool IncludeI = false,
+                                  const DominatorTree *DT, bool IncludeI = false,
                                   OrderedBasicBlock *OBB = nullptr);
 
   /// This callback is used in conjunction with PointerMayBeCaptured. In