Partially revert 9734 due to crashes in dev and canary channel.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 3e9c6c695456d0e66bdbf015ed9445aa92935f3c..c3918e634c0f060c49870744f6d4eb2def7a7d5c 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -11216,48 +11216,28 @@ class ScopeIterator {
       inlined_frame_index_(inlined_frame_index),
       function_(JSFunction::cast(frame->function())),
       context_(Context::cast(frame->context())),
-      nested_scope_chain_(4) {
+      local_done_(false),
+      at_local_(false) {
 
-    // Catch the case when the debugger stops in an internal function.
-    Handle<SharedFunctionInfo> shared_info(function_->shared());
-    if (shared_info->script() == isolate->heap()->undefined_value()) {
-      while (context_->closure() == *function_) {
-        context_ = Handle<Context>(context_->previous(), isolate_);
-      }
-      return;
-    }
-
-    // Check whether we are in global code or function code. If there is a stack
-    // slot for .result then this function has been created for evaluating
-    // global code and it is not a real function.
+    // Check whether the first scope is actually a local scope.
+    // If there is a stack slot for .result then this local scope has been
+    // created for evaluating top level code and it is not a real local scope.
     // Checking for the existence of .result seems fragile, but the scope info
     // saved with the code object does not otherwise have that information.
-    int index = shared_info->scope_info()->
+    int index = function_->shared()->scope_info()->
         StackSlotIndex(isolate_->heap()->result_symbol());
-
-    // Reparse the code and analyze the scopes.
-    ZoneScope zone_scope(isolate, DELETE_ON_EXIT);
-    Handle<Script> script(Script::cast(shared_info->script()));
-    Scope* scope;
     if (index >= 0) {
-      // Global code
-      CompilationInfo info(script);
-      info.MarkAsGlobal();
-      CHECK(ParserApi::Parse(&info));
-      CHECK(Scope::Analyze(&info));
-      scope = info.function()->scope();
-    } else {
-      // Function code
-      CompilationInfo info(shared_info);
-      CHECK(ParserApi::Parse(&info));
-      CHECK(Scope::Analyze(&info));
-      scope = info.function()->scope();
+      local_done_ = true;
+    } else if (context_->IsGlobalContext() ||
+               context_->IsFunctionContext()) {
+      at_local_ = true;
+    } else if (context_->closure() != *function_) {
+      // The context_ is a block or with or catch block from the outer function.
+      ASSERT(context_->IsWithContext() ||
+             context_->IsCatchContext() ||
+             context_->IsBlockContext());
+      at_local_ = true;
     }
-
-    // Retrieve the scope chain for the current position.
-    int statement_position =
-        shared_info->code()->SourceStatementPosition(frame_->pc());
-    scope->GetNestedScopeChain(&nested_scope_chain_, statement_position);
   }
 
   // More scopes?
@@ -11265,48 +11245,40 @@ class ScopeIterator {
 
   // Move to the next scope.
   void Next() {
-    ScopeType scope_type = Type();
-    if (scope_type == ScopeTypeGlobal) {
-      // The global scope is always the last in the chain.
-      ASSERT(context_->IsGlobalContext());
+    // If at a local scope mark the local scope as passed.
+    if (at_local_) {
+      at_local_ = false;
+      local_done_ = true;
+
+      // If the current context is not associated with the local scope the
+      // current context is the next real scope, so don't move to the next
+      // context in this case.
+      if (context_->closure() != *function_) {
+        return;
+      }
+    }
+
+    // The global scope is always the last in the chain.
+    if (context_->IsGlobalContext()) {
       context_ = Handle<Context>();
       return;
     }
-    if (nested_scope_chain_.is_empty()) {
-      context_ = Handle<Context>(context_->previous(), isolate_);
-    } else {
-      if (nested_scope_chain_.last()->HasContext()) {
-        context_ = Handle<Context>(context_->previous(), isolate_);
-      }
-      nested_scope_chain_.RemoveLast();
+
+    // Move to the next context.
+    context_ = Handle<Context>(context_->previous(), isolate_);
+
+    // If passing the local scope indicate that the current scope is now the
+    // local scope.
+    if (!local_done_ &&
+        (context_->IsGlobalContext() || context_->IsFunctionContext())) {
+      at_local_ = true;
     }
   }
 
   // Return the type of the current scope.
   ScopeType Type() {
-    if (!nested_scope_chain_.is_empty()) {
-      Handle<ScopeInfo> scope_info = nested_scope_chain_.last();
-      switch (scope_info->Type()) {
-        case FUNCTION_SCOPE:
-          ASSERT(context_->IsFunctionContext() ||
-                 !scope_info->HasContext());
-          return ScopeTypeLocal;
-        case GLOBAL_SCOPE:
-          ASSERT(context_->IsGlobalContext());
-          return ScopeTypeGlobal;
-        case WITH_SCOPE:
-          ASSERT(context_->IsWithContext());
-          return ScopeTypeWith;
-        case CATCH_SCOPE:
-          ASSERT(context_->IsCatchContext());
-          return ScopeTypeCatch;
-        case BLOCK_SCOPE:
-          ASSERT(!scope_info->HasContext() ||
-                 context_->IsBlockContext());
-          return ScopeTypeBlock;
-        case EVAL_SCOPE:
-          UNREACHABLE();
-      }
+    if (at_local_) {
+      return ScopeTypeLocal;
     }
     if (context_->IsGlobalContext()) {
       ASSERT(context_->global()->IsGlobalObject());
@@ -11332,7 +11304,6 @@ class ScopeIterator {
         return Handle<JSObject>(CurrentContext()->global());
       case ScopeIterator::ScopeTypeLocal:
         // Materialize the content of the local scope into a JSObject.
-        ASSERT(nested_scope_chain_.length() == 1);
         return MaterializeLocalScope(isolate_, frame_, inlined_frame_index_);
       case ScopeIterator::ScopeTypeWith:
         // Return the with object.
@@ -11349,28 +11320,13 @@ class ScopeIterator {
     return Handle<JSObject>();
   }
 
-  Handle<ScopeInfo> CurrentScopeInfo() {
-    if (!nested_scope_chain_.is_empty()) {
-      return nested_scope_chain_.last();
-    } else if (context_->IsBlockContext()) {
-      return Handle<ScopeInfo>(ScopeInfo::cast(context_->extension()));
-    } else if (context_->IsFunctionContext()) {
-      return Handle<ScopeInfo>(context_->closure()->shared()->scope_info());
-    }
-    return Handle<ScopeInfo>::null();
-  }
-
   // Return the context for this scope. For the local context there might not
   // be an actual context.
   Handle<Context> CurrentContext() {
-    if (Type() == ScopeTypeGlobal ||
-        nested_scope_chain_.is_empty()) {
-      return context_;
-    } else if (nested_scope_chain_.last()->HasContext()) {
-      return context_;
-    } else {
+    if (at_local_ && context_->closure() != *function_) {
       return Handle<Context>();
     }
+    return context_;
   }
 
 #ifdef DEBUG
@@ -11432,7 +11388,8 @@ class ScopeIterator {
   int inlined_frame_index_;
   Handle<JSFunction> function_;
   Handle<Context> context_;
-  List<Handle<ScopeInfo> > nested_scope_chain_;
+  bool local_done_;
+  bool at_local_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ScopeIterator);
 };
@@ -11895,65 +11852,45 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_ClearStepping) {
 
 // Creates a copy of the with context chain. The copy of the context chain is
 // is linked to the function context supplied.
-static Handle<Context> CopyNestedScopeContextChain(Isolate* isolate,
-                                                   Handle<JSFunction> function,
-                                                   Handle<Context> base,
-                                                   JavaScriptFrame* frame,
-                                                   int inlined_frame_index) {
-  HandleScope scope(isolate);
-  List<Handle<ScopeInfo> > scope_chain;
-  List<Handle<Context> > context_chain;
-
-  ScopeIterator it(isolate, frame, inlined_frame_index);
-  for (; it.Type() != ScopeIterator::ScopeTypeGlobal &&
-         it.Type() != ScopeIterator::ScopeTypeLocal ; it.Next()) {
-    ASSERT(!it.Done());
-    scope_chain.Add(it.CurrentScopeInfo());
-    context_chain.Add(it.CurrentContext());
+static Handle<Context> CopyWithContextChain(Isolate* isolate,
+                                            Handle<JSFunction> function,
+                                            Handle<Context> current,
+                                            Handle<Context> base) {
+  // At the end of the chain. Return the base context to link to.
+  if (current->IsFunctionContext() || current->IsGlobalContext()) {
+    return base;
   }
 
-  // At the end of the chain. Return the base context to link to.
-  Handle<Context> context = base;
-
-  // Iteratively copy and or materialize the nested contexts.
-  while (!scope_chain.is_empty()) {
-    Handle<ScopeInfo> scope_info = scope_chain.RemoveLast();
-    Handle<Context> current = context_chain.RemoveLast();
-    ASSERT(!(scope_info->HasContext() & current.is_null()));
-
-    if (scope_info->Type() == CATCH_SCOPE) {
-      Handle<String> name(String::cast(current->extension()));
-      Handle<Object> thrown_object(current->get(Context::THROWN_OBJECT_INDEX));
-      context =
-          isolate->factory()->NewCatchContext(function,
-                                              context,
-                                              name,
-                                              thrown_object);
-    } else if (scope_info->Type() == BLOCK_SCOPE) {
-      // Materialize the contents of the block scope into a JSObject.
-      Handle<JSObject> block_scope_object =
-          MaterializeBlockScope(isolate, current);
-      if (block_scope_object.is_null()) {
-        return Handle<Context>::null();
-      }
-      // Allocate a new function context for the debug evaluation and set the
-      // extension object.
-      Handle<Context> new_context =
-          isolate->factory()->NewFunctionContext(Context::MIN_CONTEXT_SLOTS,
-                                                 function);
-      new_context->set_extension(*block_scope_object);
-      new_context->set_previous(*context);
-      context = new_context;
-    } else {
-      ASSERT(scope_info->Type() == WITH_SCOPE);
-      ASSERT(current->IsWithContext());
-      Handle<JSObject> extension(JSObject::cast(current->extension()));
-      context =
-          isolate->factory()->NewWithContext(function, context, extension);
+  // Recursively copy the with and catch contexts.
+  HandleScope scope(isolate);
+  Handle<Context> previous(current->previous());
+  Handle<Context> new_previous =
+      CopyWithContextChain(isolate, function, previous, base);
+  Handle<Context> new_current;
+  if (current->IsCatchContext()) {
+    Handle<String> name(String::cast(current->extension()));
+    Handle<Object> thrown_object(current->get(Context::THROWN_OBJECT_INDEX));
+    new_current =
+        isolate->factory()->NewCatchContext(function,
+                                            new_previous,
+                                            name,
+                                            thrown_object);
+  } else if (current->IsBlockContext()) {
+    Handle<ScopeInfo> scope_info(ScopeInfo::cast(current->extension()));
+    new_current =
+        isolate->factory()->NewBlockContext(function, new_previous, scope_info);
+    // Copy context slots.
+    int num_context_slots = scope_info->ContextLength();
+    for (int i = Context::MIN_CONTEXT_SLOTS; i < num_context_slots; ++i) {
+      new_current->set(i, current->get(i));
     }
+  } else {
+    ASSERT(current->IsWithContext());
+    Handle<JSObject> extension(JSObject::cast(current->extension()));
+    new_current =
+        isolate->factory()->NewWithContext(function, new_previous, extension);
   }
-
-  return scope.CloseAndEscape(context);
+  return scope.CloseAndEscape(new_current);
 }
 
 
@@ -12088,11 +12025,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_DebugEvaluate) {
   if (scope_info->HasContext()) {
     function_context = Handle<Context>(frame_context->declaration_context());
   }
-  context = CopyNestedScopeContextChain(isolate,
-                                        go_between,
-                                        context,
-                                        frame,
-                                        inlined_frame_index);
+  context = CopyWithContextChain(isolate, go_between, frame_context, context);
 
   if (additional_context->IsJSObject()) {
     Handle<JSObject> extension = Handle<JSObject>::cast(additional_context);