Fix representation generalization for doubles.

BUG=
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/184393002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19599 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/property-details.h

@@ -138,7 +138,7 @@ class Representation {
 
     ASSERT(kind_ != kExternal);
     ASSERT(other.kind_ != kExternal);
-    if (IsHeapObject()) return other.IsDouble() || other.IsNone();
+    if (IsHeapObject()) return other.IsNone();
     if (kind_ == kUInteger8 && other.kind_ == kInteger8) return false;
     if (kind_ == kUInteger16 && other.kind_ == kInteger16) return false;
     return kind_ > other.kind_;

test/mjsunit/regress/regress-347909.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+var a = {y:1.5};
+a.y = 0;
+var b = a.y;
+a.y = {};
+var d = 1;
+function f() {
+  d = 0;
+  return {y: b};
+}
+f();
+f();
+%OptimizeFunctionOnNextCall(f);
+f();