Internalize strings being stored into uninitialized property cells

test/mjsunit/regress/regress-crbug-320922.js

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 // Flags: --allow-natives-syntax
 
-var string = "hello world";
-var expected = "Hello " + "world";
+var string = "internalized dummy";
+var expected = "internalized dummy";
+string = "hello world";
+expected = "Hello " + "world";
 function Capitalize() {
   %_OneByteSeqStringSetChar(0, 0x48, string);
 }
 Capitalize();
 assertEquals(expected, string);
 Capitalize();
 assertEquals(expected, string);
 
 var twobyte = "\u20ACello world";
 
 function TwoByteCapitalize() {
   %_TwoByteSeqStringSetChar(0, 0x48, twobyte);
 }
 TwoByteCapitalize();
 assertEquals(expected, twobyte);
 TwoByteCapitalize();
 assertEquals(expected, twobyte);