[turbofan] Introduce builders for property access.

This introduces a choke point in the AstGraphBuilder for property
access creation. This makes it easier to enrich all such nodes with
additional side-table or debugging information.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/1002713002

Cr-Commit-Position: refs/heads/master@{#27157}

src/compiler/ast-graph-builder.h

@@ -224,6 +224,15 @@ class AstGraphBuilder : public AstVisitor {
                           const VectorSlotPair& feedback,
                           ContextualMode mode = CONTEXTUAL);
 
+  // Builders for property loads and stores.
+  Node* BuildKeyedLoad(Node* receiver, Node* key,
+                       const VectorSlotPair& feedback);
+  Node* BuildNamedLoad(Node* receiver, Handle<Name> name,
+                       const VectorSlotPair& feedback,
+                       ContextualMode mode = NOT_CONTEXTUAL);
+  Node* BuildKeyedStore(Node* receiver, Node* key, Node* value);
+  Node* BuildNamedStore(Node* receiver, Handle<Name>, Node* value);
+
   // Builders for accessing the function context.
   Node* BuildLoadBuiltinsObject();
   Node* BuildLoadGlobalObject();