Fix bug that caused invalid code motion for certain loads instructions.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
===================================================================
--- src/hydrogen-instructions.h	(revision 7333)
+++ src/hydrogen-instructions.h	(working copy)
@@ -1407,8 +1407,9 @@
     // object. It is guaranteed to be 32 bit integer, but it can be
     // represented as either a smi or heap number.
     set_representation(Representation::Tagged());
+    SetFlag(kUseGVN);
     SetFlag(kDependsOnArrayLengths);
-    SetFlag(kUseGVN);
+    SetFlag(kDependsOnMaps);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {
@@ -1426,8 +1427,8 @@
  public:
   explicit HFixedArrayLength(HValue* value) : HUnaryOperation(value) {
     set_representation(Representation::Tagged());
+    SetFlag(kUseGVN);
     SetFlag(kDependsOnArrayLengths);
-    SetFlag(kUseGVN);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {
@@ -2257,6 +2258,7 @@
       : HBinaryOperation(left, right) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
+    SetFlag(kDependsOnMaps);
   }
 
   virtual bool EmitAtUses() {
@@ -2942,6 +2944,7 @@
         offset_(offset) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
+    SetFlag(kDependsOnMaps);
     if (is_in_object) {
       SetFlag(kDependsOnInobjectFields);
     } else {
@@ -3268,6 +3271,7 @@
       : HBinaryOperation(string, index) {
     set_representation(Representation::Integer32());
     SetFlag(kUseGVN);
+    SetFlag(kDependsOnMaps);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {
@@ -3312,6 +3316,7 @@
   explicit HStringLength(HValue* string) : HUnaryOperation(string) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
+    SetFlag(kDependsOnMaps);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {