Improve handling of property loads on the proto chain.

test/mjsunit/compiler/proto-chain-load.js

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 // Flags: --allow-natives-syntax
 
-// This is a regression test for overlapping key and value registers.
+// Test HLoadNamedField on the proto chain.
 
+var obj4 = Object.create(null, { f4: {value: 4} });
+var obj3 = Object.create(obj4, { f3: {value: 3} });
+var obj2 = Object.create(obj3, { f2: {value: 2} });
+var obj1 = Object.create(obj2, { f1: {value: 1} });
+var obj0 = Object.create(obj1, { f0: {value: 0} });
 
-var a = [0, 1, 2, 3, 4, 5];
-assertTrue(%HasFastSmiElements(a));
-a.length = (1 << 30);
-assertFalse(%HasFastSmiElements(a));
+function get4(obj) { return obj.f4; }
 
+assertEquals(4, get4(obj0));
+assertEquals(4, get4(obj0));
+%OptimizeFunctionOnNextCall(get4);
+assertEquals(4, get4(obj0));
+assertEquals(4, get4(obj0));