Improve memory usage of receiver type feedback.

src/small-pointer-list.h

Index: src/small-pointer-list.h
diff --git a/src/small-pointer-list.h b/src/small-pointer-list.h
index 6291d9ee8628d08492dc53ce30628b25066dfead..6c5ce890d2cb64fe8c437bf99c96efb144786357 100644
--- a/src/small-pointer-list.h
+++ b/src/small-pointer-list.h
@@ -44,6 +44,31 @@ class SmallPointerList {
  public:
   SmallPointerList() : data_(kEmptyTag) {}
 
+  explicit SmallPointerList(int capacity) : data_(kEmptyTag) {
+    Reserve(capacity);
+  }
+
+  void Reserve(int capacity) {
+    if (capacity < 2) return;
+    if ((data_ & kTagMask) == kListTag) {
+      if (list()->capacity() >= capacity) return;
+      int old_length = list()->length();
+      list()->AddBlock(NULL, capacity - list()->capacity());
+      list()->Rewind(old_length);
+      return;
+    }
+    PointerList* list = new PointerList(capacity);
+    if ((data_ & kTagMask) == kSingletonTag) {
+      list->Add(single_value());
+    }
+    ASSERT(IsAligned(reinterpret_cast<intptr_t>(list), kPointerAlignment));
+    data_ = reinterpret_cast<intptr_t>(list) | kListTag;
+  }
+
+  void Clear() {
+    data_ = kEmptyTag;
+  }
+
   bool is_empty() const { return length() == 0; }
 
   int length() const {