DevTools: introduce object previews experiment

third_party/WebKit/LayoutTests/inspector/console/console-format-es6-2-expected.txt

 CONSOLE MESSAGE: line 11: [object Map Iterator]
 CONSOLE MESSAGE: line 12: [object Map Iterator]
 CONSOLE MESSAGE: line 11: [object Map Iterator]
 CONSOLE MESSAGE: line 12: [object Map Iterator]
 CONSOLE MESSAGE: line 11: [object Map Iterator]
 CONSOLE MESSAGE: line 12: [object Map Iterator]
 CONSOLE MESSAGE: line 11: [object Set Iterator]
 CONSOLE MESSAGE: line 12: [object Set Iterator]
 CONSOLE MESSAGE: line 11: [object Set Iterator]
 CONSOLE MESSAGE: line 12: [object Set Iterator]
 CONSOLE MESSAGE: line 11: [object Set Iterator]
 CONSOLE MESSAGE: line 12: [object Set Iterator]
 CONSOLE MESSAGE: line 11: [object Map Iterator]
 CONSOLE MESSAGE: line 12: [object Map Iterator]
 CONSOLE MESSAGE: line 11: [object Set Iterator]
 CONSOLE MESSAGE: line 12: [object Set Iterator]
 Tests that console properly displays information about ES6 features.
 
 console-format-es6-2.html:11 MapIterator {41, Object {foo: 1}}
 console-format-es6-2.html:12 [MapIterator]
 globals[0]
 MapIterator {41, Object {foo: 1}}
 console-format-es6-2.html:11 MapIterator {42, Object {foo: 2}}
 console-format-es6-2.html:12 [MapIterator]
 globals[1]
 MapIterator {42, Object {foo: 2}}
-console-format-es6-2.html:11 MapIterator {[41, 42], [Object, Object]}
+console-format-es6-2.html:11 MapIterator {(2) [41, 42], (2) [Object, Object]}

[dgozman, 2017/01/13 02:55:41]

This looks strange, probably because we have a space between length and
contents.

What about something like this?
  Int32Array[41, 42, 43, ...(95)]
  [41, 42]
  [41, 42, ...(10 total)]

[luoe, 2017/01/13 23:20:12]

For this experiment, I propose this output:
MapIterator {Array(2), Array(2)}

Another example:
MapIterator {Int32Array(2), Object}

The MapIterator only has n=2 entries, which should be clear.  Knowing the
contents of those entries is going 2 levels deep, which I don't want to do in
this patch.

I would like to show the 2nd level preview here for entries once cutoff logic is
in place, in the next patch.

 console-format-es6-2.html:12 [MapIterator]
 globals[2]
-MapIterator {[41, 42], [Object, Object]}
+MapIterator {(2) [41, 42], (2) [Object, Object]}
 console-format-es6-2.html:11 SetIterator {41, Object {foo: 1}}
 console-format-es6-2.html:12 [SetIterator]
 globals[3]
 SetIterator {41, Object {foo: 1}}
 console-format-es6-2.html:11 SetIterator {41, Object {foo: 1}}
 console-format-es6-2.html:12 [SetIterator]
 globals[4]
 SetIterator {41, Object {foo: 1}}
-console-format-es6-2.html:11 SetIterator {[41, 41], [Object, Object]}
+console-format-es6-2.html:11 SetIterator {(2) [41, 41], (2) [Object, Object]}
 console-format-es6-2.html:12 [SetIterator]
 globals[5]
-SetIterator {[41, 41], [Object, Object]}
+SetIterator {(2) [41, 41], (2) [Object, Object]}
 console-format-es6-2.html:11 MapIterator {Object {foo: 2}}
 console-format-es6-2.html:12 [MapIterator]
 globals[6]
 MapIterator {Object {foo: 2}}
 console-format-es6-2.html:11 SetIterator {Object {foo: 1}}
 console-format-es6-2.html:12 [SetIterator]
 globals[7]
 SetIterator {Object {foo: 1}}
 Expanded all messages
 console-format-es6-2.html:11 MapIterator
     __proto__: Map Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "keys"
     [[Entries]]: Array(2)
-        0: 41
-        1: Object
+        0: 41 {value: 41}
+        1: Object {value: Object}
         length: 2
 console-format-es6-2.html:12 Array(1)
-    0: MapIterator
+    0: MapIterator {41, Object {foo: 1}}
     length: 1
     __proto__: Array(0)
 globals[0]
 MapIterator
     __proto__: Map Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "keys"
     [[Entries]]: Array(2)
-        0: 41
-        1: Object
+        0: 41 {value: 41}
+        1: Object {value: Object}
         length: 2
 console-format-es6-2.html:11 MapIterator
     __proto__: Map Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "values"
     [[Entries]]: Array(2)
-        0: 42
-        1: Object
+        0: 42 {value: 42}
+        1: Object {value: Object}
         length: 2
 console-format-es6-2.html:12 Array(1)
-    0: MapIterator
+    0: MapIterator {42, Object {foo: 2}}
     length: 1
     __proto__: Array(0)
 globals[1]
 MapIterator
     __proto__: Map Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "values"
     [[Entries]]: Array(2)
-        0: 42
-        1: Object
+        0: 42 {value: 42}
+        1: Object {value: Object}
         length: 2
 console-format-es6-2.html:11 MapIterator
     __proto__: Map Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "entries"
     [[Entries]]: Array(2)
-        0: Array(2)
-        1: Array(2)
+        0: Array(2) {value: Array(2)}
+        1: Array(2) {value: Array(2)}
         length: 2
 console-format-es6-2.html:12 Array(1)
-    0: MapIterator
+    0: MapIterator {(2) [41, 42], (2) [Object, Object]}
     length: 1
     __proto__: Array(0)
 globals[2]
 MapIterator
     __proto__: Map Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "entries"
     [[Entries]]: Array(2)
-        0: Array(2)
-        1: Array(2)
+        0: Array(2) {value: Array(2)}
+        1: Array(2) {value: Array(2)}
         length: 2
 console-format-es6-2.html:11 SetIterator
     __proto__: Set Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "values"
     [[Entries]]: Array(2)
-        0: 41
-        1: Object
+        0: 41 {value: 41}
+        1: Object {value: Object}
         length: 2
 console-format-es6-2.html:12 Array(1)
-    0: SetIterator
+    0: SetIterator {41, Object {foo: 1}}
     length: 1
     __proto__: Array(0)
 globals[3]
 SetIterator
     __proto__: Set Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "values"
     [[Entries]]: Array(2)
-        0: 41
-        1: Object
+        0: 41 {value: 41}
+        1: Object {value: Object}
         length: 2
 console-format-es6-2.html:11 SetIterator
     __proto__: Set Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "values"
     [[Entries]]: Array(2)
-        0: 41
-        1: Object
+        0: 41 {value: 41}
+        1: Object {value: Object}
         length: 2
 console-format-es6-2.html:12 Array(1)
-    0: SetIterator
+    0: SetIterator {41, Object {foo: 1}}
     length: 1
     __proto__: Array(0)
 globals[4]
 SetIterator
     __proto__: Set Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "values"
     [[Entries]]: Array(2)
-        0: 41
-        1: Object
+        0: 41 {value: 41}
+        1: Object {value: Object}
         length: 2
 console-format-es6-2.html:11 SetIterator
     __proto__: Set Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "entries"
     [[Entries]]: Array(2)
-        0: Array(2)
-        1: Array(2)
+        0: Array(2) {value: Array(2)}
+        1: Array(2) {value: Array(2)}
         length: 2
 console-format-es6-2.html:12 Array(1)
-    0: SetIterator
+    0: SetIterator {(2) [41, 41], (2) [Object, Object]}
     length: 1
     __proto__: Array(0)
 globals[5]
 SetIterator
     __proto__: Set Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 0
     [[IteratorKind]]: "entries"
     [[Entries]]: Array(2)
-        0: Array(2)
-        1: Array(2)
+        0: Array(2) {value: Array(2)}
+        1: Array(2) {value: Array(2)}
         length: 2
 console-format-es6-2.html:11 MapIterator
     __proto__: Map Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 1
     [[IteratorKind]]: "values"
     [[Entries]]: Array(1)
-        0: Object
+        0: Object {value: Object}
         length: 1
 console-format-es6-2.html:12 Array(1)
-    0: MapIterator
+    0: MapIterator {Object {foo: 2}}
     length: 1
     __proto__: Array(0)
 globals[6]
 MapIterator
     __proto__: Map Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 1
     [[IteratorKind]]: "values"
     [[Entries]]: Array(1)
-        0: Object
+        0: Object {value: Object}
         length: 1
 console-format-es6-2.html:11 SetIterator
     __proto__: Set Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 1
     [[IteratorKind]]: "values"
     [[Entries]]: Array(1)
-        0: Object
+        0: Object {value: Object}
         length: 1
 console-format-es6-2.html:12 Array(1)
-    0: SetIterator
+    0: SetIterator {Object {foo: 1}}

[dgozman, 2017/01/13 02:55:41]

This looks strange as well. Maybe just {foo: 1}?

[luoe, 2017/01/13 23:20:12]

From the proposal in my comment above, I'd like to just show "Object" for now,
as "{foo: 1}" will be 2 levels deep.

     length: 1
     __proto__: Array(0)
 globals[7]
 SetIterator
     __proto__: Set Iterator
     [[IteratorHasMore]]: true
     [[IteratorIndex]]: 1
     [[IteratorKind]]: "values"
     [[Entries]]: Array(1)
-        0: Object
+        0: Object {value: Object}
         length: 1