[parser] Skipping inner funcs: Add debug code.

There are some mysterious, unreproducible CHECK failures (inconsistent
data). Add more information onto the stack (and thus, to minidumps) for
debugging them.

BUG=v8:5516,chromium:766693

Change-Id: Ic1ebc3036957ede4e3e1c1d287479897e54e40ed
Reviewed-on: https://chromium-review.googlesource.com/677294Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48111}

src/parsing/preparsed-scope-data.cc

@@ -478,6 +478,13 @@ void ConsumedPreParsedScopeData::RestoreData(Scope* scope,
     return;
   }
 
+  if (scope_data->length() < index_ + 1) {
+    // Temporary debugging code for detecting inconsistent data. Write debug
+    // information on the stack, then crash.
+    scope_data->GetIsolate()->PushStackTraceAndDie(0xc0defee, nullptr, nullptr,
+                                                   0xc0defee);
+  }
+
   // scope_type is stored only in debug mode.
   CHECK_GE(scope_data->length(), index_ + 1);
   DCHECK_GE(scope_data->length(), index_ + 2);