Revert r13025 and r13026 (they introduced a bug on arm and regressed octane crypto).

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index e9a1e935f5e937a40dcc81aff151585389a53a55..7d46c068589bfb707a43e93d84bf5cc74e328275 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8323,9 +8323,6 @@ class Foreign: public HeapObject {
 };
 
 
-class PropertyIndex;
-
-
 // The JSArray describes JavaScript Arrays
 //  Such an array can be in one of two modes:
 //    - fast, backing storage is a FixedArray and length <= elements.length();
@@ -8379,9 +8376,6 @@ class JSArray: public JSObject {
   static const int kLengthOffset = JSObject::kHeaderSize;
   static const int kSize = kLengthOffset + kPointerSize;
 
-  static inline PropertyIndex ArrayLengthIndex();
-  STATIC_ASSERT(kLengthOffset % kPointerSize == 0);
-
  private:
   // Expand the fixed array backing of a fast-case JSArray to at least
   // the requested size.