Work around erroneous GCC report about potentially clobbered variable.

runtime/vm/flow_graph_inliner.cc

 // Copyright (c) 2013, 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/flow_graph_inliner.h"
 
 #include "vm/block_scheduler.h"
 #include "vm/compiler.h"
 #include "vm/flags.h"
 #include "vm/flow_graph.h"
@@ skipping 630 matching lines @@
                                function.optimized_instruction_count(),
                                function.optimized_call_site_count(),
                                constant_arguments));
       PRINT_INLINING_TREE("Early heuristic",
           &call_data->caller, &function, call_data->call);
       return false;
     }
 
     // Abort if this is a recursive occurrence.
     Definition* call = call_data->call;
-    const bool is_recursive_call = IsCallRecursive(unoptimized_code, call);
+    // Added 'volatile' works around a possible GCC 4.9 compiler bug.
+    volatile bool is_recursive_call = IsCallRecursive(unoptimized_code, call);
     if (is_recursive_call &&
         inlining_recursion_depth_ >= FLAG_inlining_recursion_depth_threshold) {
       TRACE_INLINING(OS::Print("     Bailout: recursive function\n"));
       PRINT_INLINING_TREE("Recursive function",
           &call_data->caller, &function, call_data->call);
       return false;
     }
 
     // Save and clear deopt id.
     const intptr_t prev_deopt_id = isolate()->deopt_id();
@@ skipping 1110 matching lines @@
         OS::Print("After Inlining of %s\n", flow_graph_->
                   parsed_function().function().ToFullyQualifiedCString());
         FlowGraphPrinter printer(*flow_graph_);
         printer.PrintBlocks();
       }
     }
   }
 }
 
 }  // namespace dart