Subzero. Uses unique_ptrs in the emit queue.

Because explicit memory ownership is awesome!

BUG=
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1804133002 .

src/IceCfg.h

diff --git a/src/IceCfg.h b/src/IceCfg.h
index f326cf3..95d79bc 100644
--- a/src/IceCfg.h
+++ b/src/IceCfg.h
@@ -174,7 +174,9 @@
   template <typename T = Assembler> T *getAssembler() const {
     return llvm::dyn_cast<T>(TargetAssembler.get());
   }
-  Assembler *releaseAssembler() { return TargetAssembler.release(); }
+  std::unique_ptr<Assembler> releaseAssembler() {
+    return std::move(TargetAssembler);
+  }
   bool hasComputedFrame() const;
   bool getFocusedTiming() const { return FocusedTiming; }
   void setFocusedTiming() { FocusedTiming = true; }