deps: cherry-pick 68e89fb from v8's upstream

Original commit message:

    This commit adds some postmortem data that is otherwise unavailable.

    I have discovered need in those values when writing:

    https://github.com/indutny/llnode

    BUG=

    Review URL: https://codereview.chromium.org/1436473002

    Cr-Commit-Position: refs/heads/master@{#31947}

This postmortem information is useful for both object inspection, and
function's context variables inspection.

Ref: https://github.com/nodejs/node/pull/3779
PR-URL: https://github.com/nodejs/node/pull/4106
Reviewed-By: bnoordhuis - Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: targos - Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: rvagg - Rod Vagg <rod@vagg.org>

deps/v8/tools/gen-postmortem-metadata.py

@@ -98,6 +98,30 @@ consts_misc = [
         'value': 'PropertyDetails::FieldIndexField::kMask' },
     { 'name': 'prop_index_shift',
         'value': 'PropertyDetails::FieldIndexField::kShift' },
+    { 'name': 'prop_representation_mask',
+        'value': 'PropertyDetails::RepresentationField::kMask' },
+    { 'name': 'prop_representation_shift',
+        'value': 'PropertyDetails::RepresentationField::kShift' },
+    { 'name': 'prop_representation_integer8',
+        'value': 'Representation::Kind::kInteger8' },
+    { 'name': 'prop_representation_uinteger8',
+        'value': 'Representation::Kind::kUInteger8' },
+    { 'name': 'prop_representation_integer16',
+        'value': 'Representation::Kind::kInteger16' },
+    { 'name': 'prop_representation_uinteger16',
+        'value': 'Representation::Kind::kUInteger16' },
+    { 'name': 'prop_representation_smi',
+        'value': 'Representation::Kind::kSmi' },
+    { 'name': 'prop_representation_integer32',
+        'value': 'Representation::Kind::kInteger32' },
+    { 'name': 'prop_representation_double',
+        'value': 'Representation::Kind::kDouble' },
+    { 'name': 'prop_representation_heapobject',
+        'value': 'Representation::Kind::kHeapObject' },
+    { 'name': 'prop_representation_tagged',
+        'value': 'Representation::Kind::kTagged' },
+    { 'name': 'prop_representation_external',
+        'value': 'Representation::Kind::kExternal' },
 
     { 'name': 'prop_desc_key',
         'value': 'DescriptorArray::kDescriptorKey' },
@@ -121,6 +145,10 @@ consts_misc = [
         'value': 'Map::ElementsKindBits::kShift' },
     { 'name': 'bit_field3_dictionary_map_shift',
         'value': 'Map::DictionaryMap::kShift' },
+    { 'name': 'bit_field3_number_of_own_descriptors_mask',
+        'value': 'Map::NumberOfOwnDescriptorsBits::kMask' },
+    { 'name': 'bit_field3_number_of_own_descriptors_shift',
+        'value': 'Map::NumberOfOwnDescriptorsBits::kShift' },
 
     { 'name': 'off_fp_context',
         'value': 'StandardFrameConstants::kContextOffset' },
@@ -139,14 +167,31 @@ consts_misc = [
         'value': 'ScopeInfo::kStackLocalCount' },
     { 'name': 'scopeinfo_idx_ncontextlocals',
         'value': 'ScopeInfo::kContextLocalCount' },
+    { 'name': 'scopeinfo_idx_ncontextglobals',
+        'value': 'ScopeInfo::kContextGlobalCount' },
     { 'name': 'scopeinfo_idx_first_vars',
         'value': 'ScopeInfo::kVariablePartIndex' },
+
+    { 'name': 'sharedfunctioninfo_start_position_mask',
+        'value': 'SharedFunctionInfo::kStartPositionMask' },
+    { 'name': 'sharedfunctioninfo_start_position_shift',
+        'value': 'SharedFunctionInfo::kStartPositionShift' },
+
+    { 'name': 'jsarray_buffer_was_neutered_mask',
+        'value': 'JSArrayBuffer::WasNeutered::kMask' },
+    { 'name': 'jsarray_buffer_was_neutered_shift',
+        'value': 'JSArrayBuffer::WasNeutered::kShift' },
 ];
 
 #
 # The following useful fields are missing accessors, so we define fake ones.
 #
 extras_accessors = [
+    'JSFunction, context, Context, kContextOffset',
+    'Context, closure_index, int, CLOSURE_INDEX',
+    'Context, global_object_index, int, GLOBAL_OBJECT_INDEX',
+    'Context, previous_index, int, PREVIOUS_INDEX',
+    'Context, min_context_slots, int, MIN_CONTEXT_SLOTS',
     'HeapObject, map, Map, kMapOffset',
     'JSObject, elements, Object, kElementsOffset',
     'FixedArray, data, uintptr_t, kHeaderSize',
@@ -162,6 +207,7 @@ extras_accessors = [
     'Map, prototype, Object, kPrototypeOffset',
     'NameDictionaryShape, prefix_size, int, kPrefixSize',
     'NameDictionaryShape, entry_size, int, kEntrySize',
+    'NameDictionary, prefix_start_index, int, kPrefixStartIndex',
     'SeededNumberDictionaryShape, prefix_size, int, kPrefixSize',
     'UnseededNumberDictionaryShape, prefix_size, int, kPrefixSize',
     'NumberDictionaryShape, entry_size, int, kEntrySize',
@@ -173,6 +219,7 @@ extras_accessors = [
     'SeqOneByteString, chars, char, kHeaderSize',
     'SeqTwoByteString, chars, char, kHeaderSize',
     'SharedFunctionInfo, code, Code, kCodeOffset',
+    'SharedFunctionInfo, scope_info, ScopeInfo, kScopeInfoOffset',
     'SlicedString, parent, String, kParentOffset',
     'Code, instruction_start, uintptr_t, kHeaderSize',
     'Code, instruction_size, int, kInstructionSizeOffset',