NaCl SDK: Remove some unused variables in url_loader.cc example

PNaCl is being upgraded to Clang 3.4, which now warns about unused
declarations inside anonymous namespaces.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3757
TEST=compile using new PNaCl toolchain
R=binji@chromium.org

Review URL: https://codereview.chromium.org/183743028

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255149 0039d316-1c4b-4281-b951-d872f2087c98

native_client_sdk/src/examples/api/url_loader/url_loader.cc

@@ -17,11 +17,6 @@
 namespace {
 const char* const kLoadUrlMethodId = "getUrl";
 static const char kMessageArgumentSeparator = ':';
-
-// Exception strings.  These are passed back to the browser when errors
-// happen during property accesses or method calls.
-const char* const kExceptionStartFailed = "URLLoaderHandler::Start() failed";
-const char* const kExceptionURLNotAString = "URL is not a string";
 }  // namespace
 
 class URLLoaderInstance : public pp::Instance {