Elide hole checks on KeyedLoads of holey double arrays.

test/mjsunit/elide-double-hole-check-2.js

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 // Flags: --allow-natives-syntax
 
-function f() {
-  var count = "";
-  count[0] --;
+function f(a, i) {
+  return a[i] + 0.5;
 }
-f();
+var arr = [0.0,,];
+assertEquals(0.5, f(arr, 0));
+assertEquals(0.5, f(arr, 0));
 %OptimizeFunctionOnNextCall(f);
-f();
+assertEquals(0.5, f(arr, 0));
+assertEquals(NaN, f(arr, 1));
+arr.__proto__ = [1.5,1.5,1.5];
+assertEquals(2, f(arr, 1));
+assertEquals(0.5, f(arr, 0));