[numeric separator] Add more tests for DecimalLiteral

Bug: v8:7317
Change-Id: I5b3072c84cf8d97c8ebfeb274d0f1134046666c9
Reviewed-on: https://chromium-review.googlesource.com/965063
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51989}

test/mjsunit/harmony/numeric-separator.js

@@ -45,6 +45,17 @@
   assertEquals(leadingZeros, 0913);
 }
 
+{
+  const dot1 = 9_1.1_3;
+  assertEquals(dot1, 91.13);
+
+  const dot2 = 1.1_3;
+  assertEquals(dot2, 1.13);
+
+  const dot3 = 1_1.21;
+  assertEquals(dot3, 11.21);
+}
+
 {
   const basic = Number('1_2_3');
   assertEquals(NaN, basic);
@@ -60,6 +71,12 @@
   assertEquals(NaN, binary);
   const leadingZeros = Number('09_1_3');
   assertEquals(NaN, leadingZeros);
+  const dot1 = Number('9_1.1_3');
+  assertEquals(NaN, dot1);
+  const dot2 = Number('1.1_3');
+  assertEquals(NaN, dot2);
+  const dot3 = Number('1_1.21');
+  assertEquals(NaN, dot3);
 }
 
 assertThrows('1_0_0_0_', SyntaxError);