[regexp] fix assertion failure when parsing close to stack overflow.

src/regexp/regexp-parser.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/regexp/regexp-parser.h"
 
 #include "src/char-predicates-inl.h"
 #include "src/factory.h"
 #include "src/isolate.h"
 #include "src/objects-inl.h"
@@ skipping 112 matching lines @@
     case '/':
       return true;
     default:
       break;
   }
   return false;
 }
 
 
 RegExpTree* RegExpParser::ReportError(Vector<const char> message) {
+  if (failed_) return NULL;  // Do not overwrite any existing error.
   failed_ = true;
   *error_ = isolate()->factory()->NewStringFromAscii(message).ToHandleChecked();
   // Zip to the end to make sure the no more input is read.
   current_ = kEndMarker;
   next_pos_ = in()->length();
   return NULL;
 }
 
 
 #define CHECK_FAILED /**/); \
@@ skipping 361 matching lines @@
               builder->AddCharacter(current());
               Advance();
             } else {
               return ReportError(CStrVector("Invalid escape"));
             }
             break;
         }
         break;
       case '{': {
         int dummy;
-        if (ParseIntervalQuantifier(&dummy, &dummy)) {
-          return ReportError(CStrVector("Nothing to repeat"));
-        }
+        bool parsed = ParseIntervalQuantifier(&dummy, &dummy CHECK_FAILED);
+        if (parsed) return ReportError(CStrVector("Nothing to repeat"));
         // fallthrough
       }
       case '}':
       case ']':
         if (unicode()) {
           return ReportError(CStrVector("Lone quantifier brackets"));
         }
       // fallthrough
       default:
         builder->AddUnicodeCharacter(current());
@@ skipping 1038 matching lines @@
     return false;
   }
   terms_.Add(new (zone()) RegExpQuantifier(min, max, quantifier_type, atom),
              zone());
   LAST(ADD_TERM);
   return true;
 }
 
 }  // namespace internal
 }  // namespace v8