Enable top exit frame profiler mode by default + Windows fixes

runtime/vm/profiler.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 "platform/utils.h"
 
 #include "vm/allocation.h"
 #include "vm/atomic.h"
 #include "vm/code_patcher.h"
 #include "vm/isolate.h"
@@ skipping 18 matching lines @@
 #endif
 DEFINE_FLAG(bool, trace_profiled_isolates, false, "Trace profiled isolates.");
 DEFINE_FLAG(charp, profile_dir, NULL,
             "Enable writing profile data into specified directory.");
 DEFINE_FLAG(int, profile_period, 1000,
             "Time between profiler samples in microseconds. Minimum 50.");
 DEFINE_FLAG(int, profile_depth, 8,
             "Maximum number stack frames walked. Minimum 1. Maximum 255.");
 DEFINE_FLAG(bool, profile_verify_stack_walk, false,
             "Verify instruction addresses while walking the stack.");
-DEFINE_FLAG(bool, profile_vm, true,
+DEFINE_FLAG(bool, profile_vm, false,
             "Always collect native stack traces.");
 
 bool Profiler::initialized_ = false;
 SampleBuffer* Profiler::sample_buffer_ = NULL;
 
 void Profiler::InitOnce() {
   // Place some sane restrictions on user controlled flags.
   SetSamplePeriod(FLAG_profile_period);
   SetSampleDepth(FLAG_profile_depth);
   Sample::InitOnce();
@@ skipping 1847 matching lines @@
     } else {
       // Collect native and Dart frames.
       ProfilerNativeStackWalker stackWalker(sample, stack_lower, stack_upper,
                                             state.pc, state.fp, state.sp);
       stackWalker.walk(isolate->heap());
     }
   }
 }
 
 }  // namespace dart