LiveEdit: implement frame dropping

src/liveedit-debugger.js

Index: src/liveedit-debugger.js
diff --git a/src/liveedit-debugger.js b/src/liveedit-debugger.js
index 2cbf0d5f259364c5ef7d593bf84e2eca24ae9a48..75effb227ff933cff1373f8c2c7e4ea36cff5102 100644
--- a/src/liveedit-debugger.js
+++ b/src/liveedit-debugger.js
@@ -389,19 +389,32 @@ Debug.LiveEditChangeScript.CheckStackActivations = function(shared_wrapper_list,
   for (var i = 0; i < shared_wrapper_list.length; i++) {
     shared_list[i] = shared_wrapper_list[i].info;
   }
-  var result = %LiveEditCheckStackActivations(shared_list);
+  var result = %LiveEditCheckAndDropActivations(shared_list, true);
+  if (result[shared_list.length]) {
+    // Extra array element may contain error message.
+    throw new liveedit.Failure(result[shared_list.length]);
+  }
+  
   var problems = new Array();
+  var dropped = new Array();
   for (var i = 0; i < shared_list.length; i++) {
-    if (result[i] == liveedit.FunctionPatchabilityStatus.FUNCTION_BLOCKED_ON_STACK) {
-      var shared = shared_list[i];
+    var shared = shared_wrapper_list[i];
+    if (result[i] == liveedit.FunctionPatchabilityStatus.REPLACED_ON_ACTIVE_STACK) {
+      dropped.push({ name: shared.function_name } );
+    } else if (result[i] != liveedit.FunctionPatchabilityStatus.AVAILABLE_FOR_PATCH) {
       var description = {
           name: shared.function_name,
-          start_pos: shared.start_position,
-          end_pos: shared.end_position
+          start_pos: shared.start_position, 
+          end_pos: shared.end_position,
+          replace_problem:
+              liveedit.FunctionPatchabilityStatus.SymbolName(result[i])
       };
       problems.push(description);
     }
   }
+  if (dropped.length > 0) {
+    change_log.push({ dropped_from_stack: dropped });
+  }
   if (problems.length > 0) {
     change_log.push( { functions_on_stack: problems } );
     throw new liveedit.Failure("Blocked by functions on stack");
@@ -410,8 +423,21 @@ Debug.LiveEditChangeScript.CheckStackActivations = function(shared_wrapper_list,
 
 // A copy of the FunctionPatchabilityStatus enum from liveedit.h
 Debug.LiveEditChangeScript.FunctionPatchabilityStatus = {
-    FUNCTION_AVAILABLE_FOR_PATCH: 0,
-    FUNCTION_BLOCKED_ON_STACK: 1
+    AVAILABLE_FOR_PATCH: 1,
+    BLOCKED_ON_ACTIVE_STACK: 2,
+    BLOCKED_ON_OTHER_STACK: 3,
+    BLOCKED_UNDER_NATIVE_CODE: 4,
+    REPLACED_ON_ACTIVE_STACK: 5
+}
+
+Debug.LiveEditChangeScript.FunctionPatchabilityStatus.SymbolName =
+    function(code) {
+  var enum = Debug.LiveEditChangeScript.FunctionPatchabilityStatus;
+  for (name in enum) {
+    if (enum[name] == code) {
+      return name;
+    }
+  }      
 }