Add pre_log option to nanobench; make this option default true in nanobench and dm.

bench/nanobench.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <ctype.h>
 
 #include "nanobench.h"
@@ skipping 1101 matching lines @@
         for (int i = 0; i < configs.count(); ++i) {
             Target* target = is_enabled(b, configs[i]);
             if (!target) {
                 continue;
             }
 
             // During HWUI output this canvas may be nullptr.
             SkCanvas* canvas = target->getCanvas();
             const char* config = target->config.name;
 
+            if (FLAGS_pre_log) {
+                SkDebugf("Running %s\t%s\n"
+                         , bench->getUniqueName()
+                         , config);
+            }
+
             target->setup();
             bench->perCanvasPreDraw(canvas);
 
             int maxFrameLag;
             int loops = target->needsFrameTiming(&maxFrameLag)
                 ? setup_gpu_bench(target, bench.get(), maxFrameLag)
                 : setup_cpu_bench(overhead, target, bench.get());
 
             if (FLAGS_ms) {
                 samples.reset();
@@ skipping 121 matching lines @@
 
     return 0;
 }
 
 #if !defined SK_BUILD_FOR_IOS
 int main(int argc, char** argv) {
     SkCommandLineFlags::Parse(argc, argv);
     return nanobench_main();
 }
 #endif