Revert of Always give class literals a block scope (patchset #2 id:20001 of https://codereview.chromium.org/1413903002/ )

Reason for revert:
[Sheriff] Breaks vector stores:
http://build.chromium.org/p/client.v8/builders/V8%20Linux64%20-%20debug%20-%20vector%20stores/builds/536

Original issue's description:
> Always give class literals a block scope
>
> Class methods always have the class scope on their scope chain in order
> to implement strong mode checks. Previously, that scope wasn't attached
> to the ClassLiteral for anonymous classes (since the scope contained
> no bindings).
>
> This patch simply puts that same scope on the ClassLiteral, anonymous
> or not, which simplifies other code that needs to reason about the scope
> of a class and its methods.
>
> Committed: https://crrev.com/cf13dda1ba25e8293ea143f33c6c5f6233a39c86
> Cr-Commit-Position: refs/heads/master@{#31371}

TBR=mstarzinger@chromium.org,adamk@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1416583002

Cr-Commit-Position: refs/heads/master@{#31373}

src/compiler/ast-graph-builder.cc

@@ -1533,15 +1533,20 @@ void AstGraphBuilder::VisitFunctionLiteral(FunctionLiteral* expr) {
 
 
 void AstGraphBuilder::VisitClassLiteral(ClassLiteral* expr) {
-  // Visit declarations and class literal in a block scope.
-  if (expr->scope()->ContextLocalCount() > 0) {
-    Node* context = BuildLocalBlockContext(expr->scope());
-    ContextScope scope(this, expr->scope(), context);
-    VisitDeclarations(expr->scope()->declarations());
+  if (expr->scope() == NULL) {
+    // Visit class literal in the same scope, no declarations.
     VisitClassLiteralContents(expr);
   } else {
-    VisitDeclarations(expr->scope()->declarations());
-    VisitClassLiteralContents(expr);
+    // Visit declarations and class literal in a block scope.
+    if (expr->scope()->ContextLocalCount() > 0) {
+      Node* context = BuildLocalBlockContext(expr->scope());
+      ContextScope scope(this, expr->scope(), context);
+      VisitDeclarations(expr->scope()->declarations());
+      VisitClassLiteralContents(expr);
+    } else {
+      VisitDeclarations(expr->scope()->declarations());
+      VisitClassLiteralContents(expr);
+    }
   }
 }
 
@@ -1639,7 +1644,8 @@ void AstGraphBuilder::VisitClassLiteralContents(ClassLiteral* expr) {
   literal = NewNode(op, literal, proto);
 
   // Assign to class variable.
-  if (expr->class_variable_proxy() != nullptr) {
+  if (expr->scope() != NULL) {
+    DCHECK_NOT_NULL(expr->class_variable_proxy());
     Variable* var = expr->class_variable_proxy()->var();
     FrameStateBeforeAndAfter states(this, BailoutId::None());
     VectorSlotPair feedback = CreateVectorSlotPair(

src/full-codegen/full-codegen.cc

@@ -1330,7 +1330,8 @@ void FullCodeGenerator::VisitClassLiteral(ClassLiteral* lit) {
 
     EmitClassDefineProperties(lit);
 
-    if (lit->class_variable_proxy() != nullptr) {
+    if (lit->scope() != NULL) {
+      DCHECK_NOT_NULL(lit->class_variable_proxy());
       EmitVariableAssignment(lit->class_variable_proxy()->var(),
                              Token::INIT_CONST, lit->ProxySlot());
     }

src/parser.cc

@@ -4895,13 +4895,15 @@ ClassLiteral* Parser::ParseClassLiteral(const AstRawString* name,
                                      block_scope->language_mode());
   }
 
-  // Note that we do not finalize this block scope because strong
-  // mode uses it as a sentinel value indicating an anonymous class.
   block_scope->set_end_position(end_pos);
 
   if (name != NULL) {
     DCHECK_NOT_NULL(proxy);
     proxy->var()->set_initializer_position(end_pos);
+  } else {
+    // Unnamed classes should not have scopes (the scope will be empty).
+    DCHECK_EQ(block_scope->num_var_or_const(), 0);
+    block_scope = nullptr;
   }
 
   return factory()->NewClassLiteral(name, block_scope, proxy, extends,