Use a monotonic clock in the implementation of Stopwatch.

runtime/vm/object.cc

 // Copyright (c) 2012, 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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 13361 matching lines @@
   INC_STAT(Thread::Current(), total_code_size, assembler->CodeSize());
 
   // Copy the instructions into the instruction area and apply all fixups.
   // Embedded pointers are still in handles at this point.
   MemoryRegion region(reinterpret_cast<void*>(instrs.EntryPoint()),
                       instrs.size());
   assembler->FinalizeInstructions(region);
   VerifiedMemory::Accept(region.start(), region.size());
   CPU::FlushICache(instrs.EntryPoint(), instrs.size());
 
-  code.set_compile_timestamp(OS::GetCurrentTraceMicros());
+  code.set_compile_timestamp(OS::GetCurrentMonotonicMicros());
   CodeObservers::NotifyAll(name,
                            instrs.EntryPoint(),
                            assembler->prologue_offset(),
                            instrs.size(),
                            optimized);
   {
     NoSafepointScope no_safepoint;
     const ZoneGrowableArray<intptr_t>& pointer_offsets =
         assembler->GetPointerOffsets();
     ASSERT(pointer_offsets.length() == pointer_offset_count);
@@ skipping 8563 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart