[arm] Share constant pool entries in snapshot.

src/assembler.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 1148 matching lines @@
       : position_(position), merged_index_(SHARING_ALLOWED), value64_(value) {}
 
   int position() const { return position_; }
   bool sharing_ok() const { return merged_index_ != SHARING_PROHIBITED; }
   bool is_merged() const { return merged_index_ >= 0; }
   int merged_index(void) const {
     DCHECK(is_merged());
     return merged_index_;
   }
   void set_merged_index(int index) {
+    DCHECK(sharing_ok());
     merged_index_ = index;
     DCHECK(is_merged());
   }
   int offset(void) const {
     DCHECK(merged_index_ >= 0);
     return merged_index_;
   }
   void set_offset(int offset) {
     DCHECK(offset >= 0);
     merged_index_ = offset;
@@ skipping 81 matching lines @@
     std::vector<ConstantPoolEntry> shared_entries;
   };
 
   Label emitted_label_;  // Records pc_offset of emitted pool
   PerTypeEntryInfo info_[ConstantPoolEntry::NUMBER_OF_TYPES];
 };
 
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_ASSEMBLER_H_