Refactor Subzero initialization and add a browser callback handler.

src/IceTranslator.h

Index: src/IceTranslator.h
diff --git a/src/IceTranslator.h b/src/IceTranslator.h
index d039148288147efbcfae3f0602fdd4df8def4952..adddc32c8d0b428bbd22d4824d9d0c49284d3c1c 100644
--- a/src/IceTranslator.h
+++ b/src/IceTranslator.h
@@ -74,7 +74,7 @@ public:
 protected:
   GlobalContext *Ctx;
   uint32_t NextSequenceNumber;
-  // Exit status of the translation. False is successful. True otherwise.
+  // ErrorCode of the translation.
   ErrorCode ErrorStatus;
 };