Basic array capacity feedback via allocation sites.

src/hydrogen.h

Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index 29885b333999f44940416a1937f1575a2d5b6ca9..b8b994e1cf005f15dd596199eb3944ca7a109dfc 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -1747,6 +1747,7 @@ class HGraphBuilder {
 
     ElementsKind kind() { return kind_; }
     HAllocate* elements_location() { return elements_location_; }
+    HValue* allocation_site() { return allocation_site_payload_; }
 
     HAllocate* AllocateEmptyArray();
     HAllocate* AllocateArray(HValue* capacity,
@@ -1774,10 +1775,7 @@ class HGraphBuilder {
     }
     HGraphBuilder* builder() { return builder_; }
     HGraph* graph() { return builder_->graph(); }
-    int initial_capacity() {
-      STATIC_ASSERT(JSArray::kPreallocatedArrayElements > 0);
-      return JSArray::kPreallocatedArrayElements;
-    }
+    HConstant* initial_capacity();
 
     HValue* EmitInternalMapCode();