Revert "Initial implementation of on-stack replacement (OSR)."

runtime/vm/assembler_ia32.h

Index: runtime/vm/assembler_ia32.h
diff --git a/runtime/vm/assembler_ia32.h b/runtime/vm/assembler_ia32.h
index df68c4615d31e3226a2eeba6568e12eedbbc8b85..7ed62a8eda7fc04105a26b82533ddaebaf9db25e 100644
--- a/runtime/vm/assembler_ia32.h
+++ b/runtime/vm/assembler_ia32.h
@@ -714,11 +714,6 @@ class Assembler : public ValueObject {
   //   .....
   void EnterDartFrame(intptr_t frame_size);
 
-  // Set up a Dart frame for a function compiled for on-stack replacement.
-  // The frame layout is a normal Dart frame, but the frame is partially set
-  // up on entry (it is the frame of the unoptimized code).
-  void EnterOsrFrame(intptr_t extra_size);
-
   // Set up a stub frame so that the stack traversal code can easily identify
   // a stub frame.
   // The stub frame layout is as follows: