Changed interface to preparser to not require pushback support.

include/v8-preparser.h

Index: include/v8-preparser.h
diff --git a/include/v8-preparser.h b/include/v8-preparser.h
index 68ce50223ec51c1b725ef1db298d2b7a8cc79c16..9425f7d46725a1b64dda1b622cbe9b5634b082a7 100644
--- a/include/v8-preparser.h
+++ b/include/v8-preparser.h
@@ -99,13 +99,6 @@ class UnicodeInputStream {
   // Returns the next Unicode code-point in the input, or a negative value when
   // there is no more input in the stream.
   virtual int32_t Next() = 0;
-
-  // Pushes a read character back into the stream, so that it will be the next
-  // to be read by Advance(). The character pushed back must be the most
-  // recently read character that hasn't already been pushed back (i.e., if
-  // pushing back more than one character, they must occur in the opposite order
-  // of the one they were read in).
-  virtual void PushBack(int32_t ch) = 0;
 };