[inspector] description for weak collections should not contain size

test/inspector/runtime/length-or-size-description.js

Index: test/inspector/runtime/length-or-size-description.js
diff --git a/test/inspector/runtime/length-or-size-description.js b/test/inspector/runtime/length-or-size-description.js
index e2c874f0c1c3b4211f3b45087f91d9860dcb13ab..b27b4b3651dee65fcfa1e0b970dbdecd51d2ed6b 100644
--- a/test/inspector/runtime/length-or-size-description.js
+++ b/test/inspector/runtime/length-or-size-description.js
@@ -12,7 +12,10 @@ Promise.all([
   testExpression("new Array()"),
   testExpression("new Array(2)"),
   testExpression("new Uint8Array()"),
-  testExpression("new Uint8Array(2)")
+  testExpression("new Uint8Array(2)"),
+  // WeakMap and WeakSet should not have size in description.
+  testExpression("new WeakMap([[{}, 42]])"),
+  testExpression("new WeakSet([{}])")
 ]).then(() => InspectorTest.completeTest());
 
 function testExpression(expression) {