Fix file.copy recipe_module to not fail if files are already equal.

scripts/slave/recipes/skia/swarm_perf.expected/Perf-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-VisualBench.json

Index: scripts/slave/recipes/skia/swarm_perf.expected/Perf-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-VisualBench.json
diff --git a/scripts/slave/recipes/skia/swarm_perf.expected/Perf-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-VisualBench.json b/scripts/slave/recipes/skia/swarm_perf.expected/Perf-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-VisualBench.json
index abc5363f6e5dcd94cc3a03169f5ba44b113adef8..c797ac718a5c9fb83c0e427ed4e21ba7d6ef5789 100644
--- a/scripts/slave/recipes/skia/swarm_perf.expected/Perf-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-VisualBench.json
+++ b/scripts/slave/recipes/skia/swarm_perf.expected/Perf-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-VisualBench.json
@@ -48,7 +48,7 @@
     "cmd": [
       "python",
       "-u",
-      "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
+      "\nimport shutil\nimport sys\n# Apparently, shutil.copy fails if files are binary-equal on *nix OSes.\n# See http://crbug.com/636168#c8.\nif hasattr(shutil, '_samefile'):\n  if shutil._samefile(sys.argv[1], sys.argv[2]):\n    sys.exit(0)\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]/skia/infra/bots/assets/skp/VERSION",
       "/path/to/tmp/"
     ],
@@ -68,7 +68,7 @@
     "cmd": [
       "python",
       "-u",
-      "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
+      "\nimport shutil\nimport sys\n# Apparently, shutil.copy fails if files are binary-equal on *nix OSes.\n# See http://crbug.com/636168#c8.\nif hasattr(shutil, '_samefile'):\n  if shutil._samefile(sys.argv[1], sys.argv[2]):\n    sys.exit(0)\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]/skia/infra/bots/assets/skimage/VERSION",
       "/path/to/tmp/"
     ],