VM: Reland Inline instance object hash code into object header on 64bit.

runtime/vm/assembler_arm.cc

Index: runtime/vm/assembler_arm.cc
diff --git a/runtime/vm/assembler_arm.cc b/runtime/vm/assembler_arm.cc
index 85bf01a8f20fb56eab59135f7a057b407cfb41e9..c51cd60a14b8ff319876a1bf3117b95251a08e31 100644
--- a/runtime/vm/assembler_arm.cc
+++ b/runtime/vm/assembler_arm.cc
@@ -3471,7 +3471,7 @@ void Assembler::TryAllocate(const Class& cls,
     ASSERT(instance_size >= kHeapObjectTag);
     AddImmediate(instance_reg, -instance_size + kHeapObjectTag);
 
-    uword tags = 0;
+    uint32_t tags = 0;
     tags = RawObject::SizeTag::update(instance_size, tags);
     ASSERT(cls.id() != kIllegalCid);
     tags = RawObject::ClassIdTag::update(cls.id(), tags);
@@ -3520,7 +3520,7 @@ void Assembler::TryAllocateArray(intptr_t cid,
 
     // Initialize the tags.
     // instance: new object start as a tagged pointer.
-    uword tags = 0;
+    uint32_t tags = 0;
     tags = RawObject::ClassIdTag::update(cid, tags);
     tags = RawObject::SizeTag::update(instance_size, tags);
     LoadImmediate(temp1, tags);