Initial implementation of on-stack replacement (OSR).

runtime/vm/compiler.h

Index: runtime/vm/compiler.h
diff --git a/runtime/vm/compiler.h b/runtime/vm/compiler.h
index 352ac4f566df0f84f0e6cd4d0ad3639160f78534..ab49c800afeb4042124a99ab90060811801fa59d 100644
--- a/runtime/vm/compiler.h
+++ b/runtime/vm/compiler.h
@@ -44,7 +44,9 @@ class Compiler : public AllStatic {
   // Generates optimized code for function.
   //
   // Returns Error::null() if there is no compilation error.
-  static RawError* CompileOptimizedFunction(const Function& function);
+  static RawError* CompileOptimizedFunction(
+      const Function& function,
+      intptr_t osr_id = Isolate::kNoDeoptId);
 
   // Generates code for given parsed function (without parsing it again) and
   // sets its code field.