Revert of Make nanobench and dm be usable from Chromium build (patchset #5 id:80001 of https://codereview.chromium.org/657373002/)

Reason for revert:
Causing breakages on Mac build.

Original issue's description:
> Make nanobench and dm be usable from Chromium build
>
> Move the app logic for each app as follows:
>
> <app>.cpp -- the file which contains main(). Embedders that compile
> their own apps, such as ios shell, upcoming Chromium dm etc, do not use this.
>
> <app>_main.cpp -- the main logic of the Skia test application. This will be
> used by Skia -compiled apps as well as embedder -compiled apps.
>
> <app>_main.h -- the API for the main logic. This will be
> used by Skia -compiled apps as well as embedder -compiled apps.
>
> This way (the upcoming) Chromium dm can setup its Chromium-specific setup
> in custom main(), and then call dm_main(), without the need of any
> SK_BUILD_FOR_XXXX defines controlling whether the tool defines main or not.
>
> BUG=skia:2992
>
> Committed: https://skia.googlesource.com/skia/+/c092d3bdab5f723576cc0346cea3ee282a9cb444

TBR=mtklein@chromium.org,mtklein@google.com,borenet@google.com,kkinnunen@nvidia.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:2992

Review URL: https://codereview.chromium.org/724073002
diff --git a/dm/DM.cpp b/dm/DM.cpp
index 08a4587..52c86d5 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -1,6 +1,7 @@
 // Main binary for DM.
 // For a high-level overview, please see dm/README.
 
+#include "CrashHandler.h"
 #include "LazyDecodeBitmap.h"
 #include "SkCommonFlags.h"
 #include "SkForceLinking.h"
@@ -186,7 +187,9 @@
     }
 }
 
+int dm_main();
 int dm_main() {
+    SetupCrashHandler();
     SkAutoGraphics ag;
     SkTaskGroup::Enabler enabled(FLAGS_threads);
 
@@ -241,3 +244,10 @@
     report_failures(failures);
     return failures.count() > 0;
 }
+
+#if !defined(SK_BUILD_FOR_IOS) && !defined(SK_BUILD_FOR_NACL)
+int main(int argc, char** argv) {
+    SkCommandLineFlags::Parse(argc, argv);
+    return dm_main();
+}
+#endif