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

scripts/slave/recipes/bisection/android_bisect.expected/basic_perf_tryjob_android_nexus5_perf_bisect.json

Index: scripts/slave/recipes/bisection/android_bisect.expected/basic_perf_tryjob_android_nexus5_perf_bisect.json
diff --git a/scripts/slave/recipes/bisection/android_bisect.expected/basic_perf_tryjob_android_nexus5_perf_bisect.json b/scripts/slave/recipes/bisection/android_bisect.expected/basic_perf_tryjob_android_nexus5_perf_bisect.json
index 7f80c18e0a3cd477b595a742cafb60f7fda4f62d..ce00d8777b811e68fed1e8a483c9bf70c1ab63cb 100644
--- a/scripts/slave/recipes/bisection/android_bisect.expected/basic_perf_tryjob_android_nexus5_perf_bisect.json
+++ b/scripts/slave/recipes/bisection/android_bisect.expected/basic_perf_tryjob_android_nexus5_perf_bisect.json
@@ -667,7 +667,7 @@
     "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",
       "[BUILDER_CACHE]/android_nexus5_perf_bisect/src/chrome/VERSION",
       "/path/to/tmp/"
     ],
@@ -1016,7 +1016,7 @@
     "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",
       "[BUILDER_CACHE]/android_nexus5_perf_bisect/src/chrome/VERSION",
       "/path/to/tmp/"
     ],
@@ -1304,7 +1304,7 @@
     "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",
       "[BUILDER_CACHE]/android_nexus5_perf_bisect/src/chrome/VERSION",
       "/path/to/tmp/"
     ],