Initialize offsets also for the unreachable branch (clang -Wsometimes-uninitialized).

runtime/vm/regexp_assembler.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/regexp_assembler.h"
 
 #include "vm/bit_vector.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 1780 matching lines @@
   return LoadCodeUnitsAt(index, 1);
 }
 
 
 Value* IRRegExpMacroAssembler::LoadCodeUnitsAt(LocalVariable* index,
                                                intptr_t characters) {
   // Bind the pattern as the load receiver.
   Value* pattern_val = BindLoadLocal(*string_param_);
   if (RawObject::IsExternalStringClassId(specialization_cid_)) {
     // The data of an external string is stored through two indirections.
-    intptr_t external_offset;
-    intptr_t data_offset;
+    intptr_t external_offset = 0;
+    intptr_t data_offset = 0;
     if (specialization_cid_ == kExternalOneByteStringCid) {
       external_offset = ExternalOneByteString::external_data_offset();
       data_offset = RawExternalOneByteString::ExternalData::data_offset();
     } else if (specialization_cid_ == kExternalTwoByteStringCid) {
       external_offset = ExternalTwoByteString::external_data_offset();
       data_offset = RawExternalTwoByteString::ExternalData::data_offset();
     } else {
       UNREACHABLE();
     }
     // This pushes untagged values on the stack which are immediately consumed:
@@ skipping 13 matching lines @@
       index_val,
       characters,
       specialization_cid_,
       Scanner::kNoSourcePos));
 }
 
 
 #undef __
 
 }  // namespace dart