Fix crash in observatory: stub code do not have inlined intervals information.

runtime/vm/stub_code_x64.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/globals.h"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 1174 matching lines @@
   __ incl(FieldAddress(func_reg, Function::usage_counter_offset()));
 }
 
 
 // Loads function into 'temp_reg', preserves 'ic_reg'.
 void StubCode::GenerateUsageCounterIncrement(Assembler* assembler,
                                              Register temp_reg) {
   Register ic_reg = RBX;
   Register func_reg = temp_reg;
   ASSERT(ic_reg != func_reg);
+  __ Comment("Increment function counter");
   __ movq(func_reg, FieldAddress(ic_reg, ICData::owner_offset()));
   __ incl(FieldAddress(func_reg, Function::usage_counter_offset()));
 }
 
 
 // Note: RBX must be preserved.
 // Attempt a quick Smi operation for known operations ('kind'). The ICData
 // must have been primed with a Smi/Smi check that will be used for counting
 // the invocations.
 static void EmitFastSmiOp(Assembler* assembler,
@@ skipping 863 matching lines @@
 
   __ movq(left, Address(RSP, 2 * kWordSize));
   __ movq(right, Address(RSP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64