LibJS: Handle exception in for loop test execution

Libraries/LibJS/Tests/for-head-errors.js

@@ -0,0 +1,36 @@
+load("test-common.js");
+
+try {
+    assertThrowsError(() => {
+        for (var i = foo; i < 100; ++i) {
+            assertNotReached();
+        }
+    }, {
+        error: ReferenceError,
+        message: "'foo' not known"
+    });
+
+    assertThrowsError(() => {
+        for (var i = 0; i < foo; ++i) {
+            assertNotReached();
+        }
+    }, {
+        error: ReferenceError,
+        message: "'foo' not known"
+    });
+
+    var loopCount = 0;
+    assertThrowsError(() => {
+        for (var i = 0; i < 100; ++foo) {
+            loopCount++;
+        }
+    }, {
+        error: ReferenceError,
+        message: "'foo' not known"
+    });
+    assert(loopCount === 1);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}