[diagnostics] Fix incorrect check for MIN_CONTEXT_SLOTS

MIN_CONTEXT_SLOTS is set to be equals to EXTENSION_INDEX, which is 2,
see
https://source.chromium.org/chromium/chromium/src/+/main:v8/src/objects/contexts.h;l=519;drc=bb32a2dd632d7350dfb722c9b4ffe4d6e3633225
We check for the scope's ContextHeaderLength instead, and handle
both cases where there is an extension slot or not.

Change-Id: I0fe46cb49bfcd4b8321f777d47e375e0fd204d00
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3085626
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76237}

src/diagnostics/gdb-jit.cc

@@ -1092,7 +1092,7 @@ class DebugInfoSection : public DebugSection {
       int params = scope.ParameterCount();
       int context_slots = scope.ContextLocalCount();
       // The real slot ID is internal_slots + context_slot_id.
-      int internal_slots = Context::MIN_CONTEXT_SLOTS;
+      int internal_slots = scope.ContextHeaderLength();
       int current_abbreviation = 4;
 
       for (int param = 0; param < params; ++param) {
@@ -1109,7 +1109,7 @@ class DebugInfoSection : public DebugSection {
       }
 
       // See contexts.h for more information.
-      DCHECK_EQ(Context::MIN_CONTEXT_SLOTS, 3);
+      DCHECK(internal_slots == 2 || internal_slots == 3);
       DCHECK_EQ(Context::SCOPE_INFO_INDEX, 0);
       DCHECK_EQ(Context::PREVIOUS_INDEX, 1);
       DCHECK_EQ(Context::EXTENSION_INDEX, 2);
@@ -1117,8 +1117,10 @@ class DebugInfoSection : public DebugSection {
       w->WriteString(".scope_info");
       w->WriteULEB128(current_abbreviation++);
       w->WriteString(".previous");
-      w->WriteULEB128(current_abbreviation++);
-      w->WriteString(".extension");
+      if (internal_slots == 3) {
+        w->WriteULEB128(current_abbreviation++);
+        w->WriteString(".extension");
+      }
 
       for (int context_slot = 0; context_slot < context_slots; ++context_slot) {
         w->WriteULEB128(current_abbreviation++);