Reapply "Save and restore feedback from JIT."

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
diff --git a/runtime/include/dart_api.h b/runtime/include/dart_api.h
index e1092cc59ac6f51ee368ffe0b327e1f8a8642b88..43b9c17260d3091ff14171b34e873fd459e1dd99 100644
--- a/runtime/include/dart_api.h
+++ b/runtime/include/dart_api.h
@@ -3185,6 +3185,22 @@ DART_EXPORT Dart_Port Dart_ServiceWaitForLoadPort();
  * ==============
  */
 
+/**
+ * Saves a serialized version of the information collected for use by the
+ * optimizing compiler, such as type feedback and usage counters. When this
+ * information is passed to Dart_Precompile, the AOT compiler may use it to
+ * produce faster and smaller code. The feedback is only used if the JIT that
+ * created it and the AOT compiler consuming it
+ *   - are running the same Dart program
+ *   - are built from the same version of the VM
+ *   - agree on whether type checks and assertions are enabled
+ *
+ * \return Returns an error handler if the VM was built in a mode that does not
+ * support saving JIT feedback.
+ */
+DART_EXPORT Dart_Handle Dart_SaveJITFeedback(uint8_t** buffer,
+                                             intptr_t* buffer_length);
+
 
 typedef struct {
   const char* library_uri;
@@ -3214,7 +3230,10 @@ typedef struct {
  * constructors was encountered.
  */
 DART_EXPORT Dart_Handle
-Dart_Precompile(Dart_QualifiedFunctionName entry_points[], bool reset_fields);
+Dart_Precompile(Dart_QualifiedFunctionName entry_points[],
+                bool reset_fields,
+                uint8_t* jit_feedback,
+                intptr_t jit_feedback_length);
 
 
 /**