Revert 194740 "Explicitly pass "--diff-cmd diff" to "svn diff", ..."

On Windows, I got the following error:
f:\src\chrome2\src>gcl commit n3d2
Loaded authentication cookies from C:\Users\jabdelmalek/.codereview_upload_cookies
Running presubmit commit checks ...
  checking owners took a long time: 906ms
Got an exception
Command svn diff --diff-cmd diff --config-dir c:\users\jabdel~1\appdata\local\temp\tmpu7bui5 content\browser\web_content
s\web_contents_impl.cc returned non-zero exit status 1 in f:\src\chrome2\src
Index: content/browser/web_contents/web_contents_impl.cc
===================================================================

svn: Can't start process 'diff': The system cannot find the file specified.

> Explicitly pass "--diff-cmd diff" to "svn diff", for users who have set some other diff tool.
> 
> Review URL: https://chromiumcodereview.appspot.com/14130006

TBR=pkasting@chromium.org

Review URL: https://codereview.chromium.org/13877013

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@194945 0039d316-1c4b-4281-b951-d872f2087c98

scm.py

@@ -803,8 +803,7 @@ class SVN(object):
   @staticmethod
   def _DiffItemInternal(filename, cwd, info, bogus_dir, full_move, revision):
     """Grabs the diff data."""
-    command = ["diff", "--diff-cmd", "diff", "--config-dir", bogus_dir,
-               filename]
+    command = ["diff", "--config-dir", bogus_dir, filename]
     if revision:
       command.extend(['--revision', revision])
     data = None
@@ -916,8 +915,7 @@ class SVN(object):
               # revision the file was deleted.
               srcinfo = {'Revision': rev}
             if (srcinfo.get('Revision') != rev and
-                SVN.Capture(['diff', '--diff-cmd', 'diff', '-r',
-                             '%d:head' % rev, srcurl], cwd)):
+                SVN.Capture(['diff', '-r', '%d:head' % rev, srcurl], cwd)):
               metaheaders.append("#$ svn cp -r %d %s %s "
                                  "### WARNING: note non-trunk copy\n" %
                                  (rev, src, filename))