diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/ion/bug908903.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/ion/bug908903.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,54 @@
+
+function f(x) {
+    return x + 1;
+}
+
+setJitCompilerOption("ion.usecount.trigger", 2);
+setJitCompilerOption("baseline.usecount.trigger", 0);
+
+assertEq(f(1), 2);     // usecount == 1 => eagerly compile with baseline.
+assertEq(f(0.5), 1.5); // usecount == 2 => normaly compile with ion.
+                       //                  invalidate for unexpect output.
+
+
+function normal() {
+    setJitCompilerOption("ion.usecount.trigger", 8);
+    setJitCompilerOption("baseline.usecount.trigger", 5);
+}
+
+function eager() {
+    setJitCompilerOption("ion.usecount.trigger", 0);
+}
+
+function h(x) {
+    return x + 1;
+}
+
+function g(x) {
+    normal();
+    return h(x) + 1;
+}
+
+normal();
+for (var i = 0; i < 10; i++) {
+    eager();
+    assertEq(g(i), i + 2);
+}
+
+
+// Check for wrong arguments.
+try {
+    setJitCompilerOption("not.an.option", 51);
+    assertEq(false, true);
+} catch (x) { }
+
+try {
+    var ion = { usecount: { trigger: null } };
+    setJitCompilerOption(ion.usecount.trigger, 42);
+    assertEq(false, true);
+} catch (x) { }
+
+try {
+    setJitCompilerOption("ion.usecount.trigger", "32");
+    assertEq(false, true);
+} catch (x) { }