[postmortem] add metadata for the new DescriptorArray layout

R=yangguo@chromium.org

Ref: https://github.com/nodejs/llnode/issues/255
Change-Id: Icda271123375db5c381fe1d1bba13dcc26f26d7c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1832311Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64169}

BUILD.gn

@@ -935,6 +935,8 @@ action("postmortem-metadata") {
     "src/objects/code.h",
     "src/objects/data-handler.h",
     "src/objects/data-handler-inl.h",
+    "src/objects/descriptor-array.h",
+    "src/objects/descriptor-array-inl.h",
     "src/objects/feedback-cell.h",
     "src/objects/feedback-cell-inl.h",
     "src/objects/fixed-array-inl.h",

tools/gen-postmortem-metadata.py

@@ -283,6 +283,7 @@ extras_accessors = [
     'Code, instruction_start, uintptr_t, kHeaderSize',
     'Code, instruction_size, int, kInstructionSizeOffset',
     'String, length, int32_t, kLengthOffset',
+    'DescriptorArray, header_size, uintptr_t, kHeaderSize',
 ];
 
 #
@@ -293,7 +294,8 @@ extras_accessors = [
 expected_classes = [
     'ConsString', 'FixedArray', 'HeapNumber', 'JSArray', 'JSFunction',
     'JSObject', 'JSRegExp', 'JSPrimitiveWrapper', 'Map', 'Oddball', 'Script',
-    'SeqOneByteString', 'SharedFunctionInfo', 'ScopeInfo', 'JSPromise'
+    'SeqOneByteString', 'SharedFunctionInfo', 'ScopeInfo', 'JSPromise',
+    'DescriptorArray'
 ];