Collect samples for background threads.

runtime/vm/precompiler.cc

 // Copyright (c) 2015, 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/precompiler.h"
 
 #include "vm/aot_optimizer.h"
 #include "vm/assembler.h"
 #include "vm/ast_printer.h"
 #include "vm/branch_optimizer.h"
@@ skipping 2652 matching lines @@
     return error.raw();
   }
   UNREACHABLE();
   return Error::null();
 }
 
 
 RawError* Precompiler::CompileFunction(Thread* thread,
                                        const Function& function) {
   VMTagScope tagScope(thread, VMTag::kCompileUnoptimizedTagId);
-  TIMELINE_FUNCTION_COMPILATION_DURATION(thread, "Function", function);
+  TIMELINE_FUNCTION_COMPILATION_DURATION(thread, "CompileFunction", function);
 
   CompilationPipeline* pipeline =
       CompilationPipeline::New(thread->zone(), function);
 
   ASSERT(FLAG_precompiled_mode);
   const bool optimized = function.IsOptimizable();  // False for natives.
   return PrecompileFunctionHelper(pipeline, function, optimized);
 }
 
 #endif  // DART_PRECOMPILER
 
 }  // namespace dart