Don't create bookmark files on OSX that start with a dot.

When creating a bookmark file by draging and droping the URL to the desktop
chromium uses the page title for the filename. In cases where the title starts
with a dot the webloc file will also start with a dot. Since files starting
with a dot are considered hidden and not shown by e.g. the Finder users won't
see the expected resulting file. To circumvent this a dot as the first
character is handled like any other character not allowed in a filename and
gets replaced by a hyphen.

BUG=138917
TEST=Paste "data:text/html,<title>. . . hey!</title>" into the Omnibox and drag
  and drop the URL to the desktop.

Review URL: https://codereview.chromium.org/1118813005

Cr-Commit-Position: refs/heads/master@{#333649}

AUTHORS

@@ -235,6 +235,7 @@ James Choi <jchoi42@pha.jhu.edu>
 James Vega <vega.james@gmail.com>
 James Wei <james.wei@intel.com>
 James Willcox <jwillcox@litl.com>
+Jan Sauer <jan@jansauer.de>
 Janwar Dinata <j.dinata@gmail.com>
 Jared Shumway <jaredshumway94@gmail.com>
 Jared Sohn <jared.sohn@gmail.com>

chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_cell.mm

@@ -722,11 +722,11 @@ static BOOL FileAlreadyExists(NSURL* base, NSString* name) {
 
 // Takes a destination URL, a suggested file name, & an extension (eg .webloc).
 // Returns the complete file name with extension you should use.
-// The name returned will not contain /, : or ?, will not be longer than
-// kMaxNameLength + length of extension, and will not be a file name that
-// already exists in that directory. If necessary it will try appending a space
-// and a number to the name (but before the extension) trying numbers up to and
-// including kMaxIndex.
+// The name returned will not contain /, : or ?, will not start with a dot,
+// will not be longer than kMaxNameLength + length of extension, and will not
+// be a file name that already exists in that directory. If necessary it will
+// try appending a space and a number to the name (but before the extension)
+// trying numbers up to and including kMaxIndex.
 // If the function gives up it returns nil.
 static NSString* UnusedLegalNameForNewDropFile(NSURL* saveLocation,
                                                NSString *fileName,
@@ -741,6 +741,11 @@ static NSString* UnusedLegalNameForNewDropFile(NSURL* saveLocation,
                                                          withString:@"-"];
   filteredName = [filteredName stringByReplacingOccurrencesOfString:@"?"
                                                          withString:@"-"];
+  filteredName =
+      [filteredName stringByReplacingOccurrencesOfString:@"."
+                                              withString:@"-"
+                                                 options:0
+                                                   range:NSMakeRange(0,1)];
 
   if ([filteredName length] > kMaxNameLength)
     filteredName = [filteredName substringToIndex:kMaxNameLength];