SKPs-as-benches in nanobench

This is meant to replace bench_pictures.

CQ_EXTRA_TRYBOTS=tryserver.skia:Build-Mac10.7-Clang-Arm7-Release-iOS-Trybot

BUG=skia:
R=bsalomon@google.com, jcgregorio@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/425393004
diff --git a/dm/DM.cpp b/dm/DM.cpp
index fd15eef..76dc414 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -46,8 +46,6 @@
                "If a file, compare generated images against JSON expectations at this path."
 );
 
-DEFINE_string(skps, "", "Directory to read skps from.");
-
 DEFINE_bool(gms, true, "Run GMs?");
 DEFINE_bool(tests, true, "Run tests?");
 DEFINE_bool(reportUsedChars, false, "Output test font construction data to be pasted into"
@@ -247,7 +245,7 @@
         sk_tool_utils::report_used_chars();
     }
 #endif
-    
+
     SkTArray<SkString> failures;
     reporter.getFailures(&failures);
     report_failures(failures);