Mono and x64 Firefox exception: 'Could not locate amd64'

[arthot]

I ran into a problem on mono 3.12.1, centos 6.6 (x64) with firefox 38, but I suppose that the problem is global for Firefox x64:

 
OpenQA.Selenium.WebDriverException : Could not locate amd64: native events will not work.
  at OpenQA.Selenium.Firefox.FirefoxBinary.ExtractAndCheck (OpenQA.Selenium.Firefox.FirefoxProfile profile, System.String noFocusSoName, System.String libraryPath32Bit, System.String libraryPath64Bit) [0x00000] in :0
  at OpenQA.Selenium.Firefox.FirefoxBinary.ModifyLinkLibraryPath (OpenQA.Selenium.Firefox.FirefoxProfile profile) [0x00000] in :0
  at OpenQA.Selenium.Firefox.FirefoxBinary.StartProfile (OpenQA.Selenium.Firefox.FirefoxProfile profile, System.String[] commandLineArguments) [0x00000] in :0
  at OpenQA.Selenium.Firefox.FirefoxDriverServer.Start () [0x00000] in :0
  at OpenQA.Selenium.Firefox.FirefoxDriverCommandExecutor.Execute (OpenQA.Selenium.Remote.Command commandToExecute) [0x00000] in :0
  at OpenQA.Selenium.Remote.RemoteWebDriver.Execute (System.String driverCommandToExecute, System.Collections.Generic.Dictionary`2 parameters) [0x00000] in :0
  at OpenQA.Selenium.Remote.RemoteWebDriver.StartSession (ICapabilities desiredCapabilities) [0x00000] in :0
  at OpenQA.Selenium.Remote.RemoteWebDriver..ctor (ICommandExecutor commandExecutor, ICapabilities desiredCapabilities) [0x00000] in :0
  at OpenQA.Selenium.Firefox.FirefoxDriver..ctor (OpenQA.Selenium.Firefox.FirefoxBinary binary, OpenQA.Selenium.Firefox.FirefoxProfile profile, ICapabilities capabilities, TimeSpan commandTimeout) [0x00000] in :0
  at OpenQA.Selenium.Firefox.FirefoxDriver..ctor (OpenQA.Selenium.Firefox.FirefoxBinary binary, OpenQA.Selenium.Firefox.FirefoxProfile profile, TimeSpan commandTimeout) [0x00000] in :0

After some investigations in source code of firefox driver I detected potential bug:
https://github.com/SeleniumHQ/selenium/blob/master/dotnet/src/webdriver/Firefox/FirefoxBinary.cs#L346

private void ModifyLinkLibraryPath(FirefoxProfile profile)
        {
            // Extract x_ignore_nofocus.so from x86, amd64 directories inside
            // the jar into a real place in the filesystem and change LD_LIBRARY_PATH
            // to reflect that.
            string existingLdLibPath = Environment.GetEnvironmentVariable("LD_LIBRARY_PATH");

            // The returned new ld lib path is terminated with ':'
            string newLdLibPath = ExtractAndCheck(profile, NoFocusLibraryName, "x86", "amd64");
            if (!string.IsNullOrEmpty(existingLdLibPath))
            {
                newLdLibPath += existingLdLibPath;
            }

            this.SetEnvironmentProperty("LD_LIBRARY_PATH", newLdLibPath);

            // Set LD_PRELOAD to x_ignore_nofocus.so - this will be taken automagically
            // from the LD_LIBRARY_PATH
            this.SetEnvironmentProperty("LD_PRELOAD", NoFocusLibraryName);
        }

Previous method is trying to extract 'x_ignore_nofocus.so' file from WebDriver.FirefoxNoFocus.x86.dll and WebDriver.FirefoxNoFocus.amd64.dll.
But according build.desc
there is no fileWebDriver.FirefoxNoFocus.amd64.dll, but only WebDriver.FirefoxNoFocus.x64.dll.
So 'x_ignore_nofocus.so' file for x64 Firefox cannot be extracted and driver throw exception

I could not build the project from sources, so I just changed "amd64" to "x64" at this line

string newLdLibPath = ExtractAndCheck(profile, NoFocusLibraryName, "x86", "amd64");

through ILSpy in WebDriver.dll, and after that my test worked fine on CentOS.