Ship Symbol.prototype.description

Intent to ship:
https://groups.google.com/forum/#!msg/v8-users/9U2kEQw8pb8/Sn91yUx5BQAJ

Bug: v8:7807
Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ia9e73495b08b432371dfb0ccc571af969ae4d59f
Reviewed-on: https://chromium-review.googlesource.com/1107210
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53933}

src/flag-definitions.h

@@ -227,8 +227,7 @@ DEFINE_IMPLICATION(harmony_class_fields, harmony_private_fields)
   V(harmony_public_fields, "harmony public fields in class literals")      \
   V(harmony_private_fields, "harmony private fields in class literals")    \
   V(harmony_numeric_separator, "harmony numeric separator between digits") \
-  V(harmony_string_matchall, "harmony String.prototype.matchAll")          \
-  V(harmony_symbol_description, "harmony Symbol.prototype.description")
+  V(harmony_string_matchall, "harmony String.prototype.matchAll")
 
 // Features that are shipping (turned on by default, but internal flag remains).
 #define HARMONY_SHIPPING(V)                                              \
@@ -239,7 +238,8 @@ DEFINE_IMPLICATION(harmony_class_fields, harmony_private_fields)
   V(harmony_bigint, "harmony arbitrary precision integers")              \
   V(harmony_dynamic_import, "harmony dynamic import")                    \
   V(harmony_array_prototype_values, "harmony Array.prototype.values")    \
-  V(harmony_array_flat, "harmony Array.prototype.{flat,flatMap}")
+  V(harmony_array_flat, "harmony Array.prototype.{flat,flatMap}")        \
+  V(harmony_symbol_description, "harmony Symbol.prototype.description")
 
 // Once a shipping feature has proved stable in the wild, it will be dropped
 // from HARMONY_SHIPPING, all occurrences of the FLAG_ variable are removed,

src/inspector/injected-script-source.js

@@ -401,9 +401,12 @@ InjectedScript.prototype = {
                     var isAccessorProperty = descriptor && ("get" in descriptor || "set" in descriptor);
                     if (accessorPropertiesOnly && !isAccessorProperty)
                         continue;
-                    if (descriptor && "get" in descriptor && "set" in descriptor && name !== "__proto__" &&
+                    // Special case for Symbol.prototype.description where the receiver of the getter is not an actual object.
+                    // Should only occur for nested previews.
+                    var isSymbolDescription = isSymbol(object) && name === 'description';
+                    if (isSymbolDescription || (descriptor && "get" in descriptor && "set" in descriptor && name !== "__proto__" &&
                             InjectedScriptHost.formatAccessorsAsProperties(object, descriptor.get) &&
-                            !doesAttributeHaveObservableSideEffectOnGet(object, name)) {
+                            !doesAttributeHaveObservableSideEffectOnGet(object, name))) {
                         descriptor.value = object[property];
                         descriptor.isOwn = true;
                         delete descriptor.get;

test/inspector/debugger/object-preview-internal-properties-expected.txt

@@ -30,6 +30,11 @@ expression: Object(Symbol(42))
         description : Symbol
         overflow : false
         properties : [
+            [0] : {
+                name : description
+                type : string
+                value : 42
+            }
         ]
         type : object
     }