Improve internal compiler API so that OSR code is never installed on function.

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 2239799140a8983cd3d7bf3ae7e781314fe23db2..0314d770120306de871a98e63cb2b55bb1f069fe 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -2293,7 +2293,7 @@ class Function : public Object {
 
   // Not thread-safe; must be called in the main thread.
   // Sets function's code and code's function.
-  void InstallOptimizedCode(const Code& code, bool is_osr) const;
+  void InstallOptimizedCode(const Code& code) const;
   void AttachCode(const Code& value) const;
   void SetInstructions(const Code& value) const;
   void ClearCode() const;
@@ -2301,6 +2301,12 @@ class Function : public Object {
   // Disables optimized code and switches to unoptimized code.
   void SwitchToUnoptimizedCode() const;
 
+  // Ensures that the function has code. If there is no code it compiles the
+  // unoptimized version of the code.  If the code contains errors, it calls
+  // Exceptions::PropagateError and does not return.  Normally returns the
+  // current code, whether it is optimized or unoptimized.
+  RawCode* EnsureHasCode() const;
+
   // Disables optimized code and switches to unoptimized code (or the lazy
   // compilation stub).
   void SwitchToLazyCompiledUnoptimizedCode() const;