Add a bitcode parser constructor for parallel parsing.

include/llvm/Bitcode/NaCl/NaClBitcodeParser.h

Index: include/llvm/Bitcode/NaCl/NaClBitcodeParser.h
diff --git a/include/llvm/Bitcode/NaCl/NaClBitcodeParser.h b/include/llvm/Bitcode/NaCl/NaClBitcodeParser.h
index 5efd7df19d06b394313f0691523ddb20eb477c31..e48aebd5e0123de3b734643f948ae43a4b032a25 100644
--- a/include/llvm/Bitcode/NaCl/NaClBitcodeParser.h
+++ b/include/llvm/Bitcode/NaCl/NaClBitcodeParser.h
@@ -597,9 +597,10 @@ protected:
   // The error stream to use if non-null (uses errs() if null).
   raw_ostream *ErrStream;
 
-  // Creates a block parser to parse the block associated with the
-  // bitcode entry that defines the beginning of a block. This
-  // instance actually parses the corresponding block.
+  // Creates a block parser to parse the block associated with the bitcode entry
+  // that defines the beginning of a block. This instance actually parses the
+  // corresponding block. Inherits the bitstream cursor from the
+  // EnclosingParser.
   NaClBitcodeParser(unsigned BlockID, NaClBitcodeParser *EnclosingParser)
       : EnclosingParser(EnclosingParser),
         Block(BlockID, EnclosingParser->Record),
@@ -608,6 +609,19 @@ protected:
         ErrStream(EnclosingParser->ErrStream)
   {}
 
+  // Same as above, but use the supplied bitstream cursor (instead of
+  // inheriting from the enclosing parser). This constructor allows
+  // parallel parsing of subblocks, by allowing the caller to generate
+  // a different Cursor for each block to be parsed in parallel.
+  NaClBitcodeParser(unsigned BlockID, NaClBitcodeParser *EnclosingParser,
+                    NaClBitstreamCursor &Cursor)
+      : EnclosingParser(EnclosingParser),
+        Block(BlockID, Cursor),
+        Record(Block),
+        Listener(EnclosingParser->Listener),
+        ErrStream(EnclosingParser->ErrStream)
+  {}
+
   /// Defines the listener for this block, and all enclosing blocks,
   /// to be the given listener. Should be set in the constructor.
   void SetListener(NaClBitcodeParserListener* UseListener) {