Handle network errors better

With this, we make an attempt to convert Java exceptions to Gecko network errors, and I also refactored this a bit.

Wladimir came up with the following mapping in the review:
- ConnectException, NoRouteToHostException, PortUnreachableException => NS_ERROR_CONNECTION_REFUSED
- MalformedURLException, URISyntaxException => NS_ERROR_MALFORMED_URI
- SocketTimeoutException => NS_ERROR_NET_TIMEOUT
- UnknownHostException => NS_ERROR_UNKNOWN_HOST

He also sugggested to add more constants to WebRequest to report SSL errors properly:
- SSLHandshakeException => SSL_ERROR_BAD_SERVER (0x805A2FF9)
- SSLKeyException => SSL_ERROR_WRONG_CERTIFICATE (0x805A2FF5)
- SSLPeerUnverifiedException => SSL_ERROR_BAD_CLIENT (0x805A2FFA)
- SSLProtocolException => SEC_ERROR_BAD_SIGNATURE (0x0x805A1FF6)

I went through the docs of the involved functions and the only mappings I could come up with based on that are those I added in this patch. For instance, HttpUrlConnection.connect() just throws an IOException. Many of the exceptions above derive from IOException, but it's not really documented what we can expect here, so this really needs proper testing of all use cases.

Since we need to get this branch merged, I'd rather not do that now and stick to the known mappings. If you want, I'll create a follow-up issue for this.

[Wladimir Palant, 2013-11-22 17:51:03]

LGTM with the issue below addressed.

http://codereview.adblockplus.org/5668574207148032/diff/5629499534213120/jni/...
File jni/AndroidWebRequest.cpp (right):

http://codereview.adblockplus.org/5668574207148032/diff/5629499534213120/jni/...
jni/AndroidWebRequest.cpp:52: return ("Java Exception: " + message).c_str();
You are creating a temporary std::string instance here and returning a reference
to its buffer - this will likely crash. You should add "Java Exception: " when
you are initializing the message variable in the constructor, this way there
shouldn't be any trouble.

[Felix Dahlke, 2013-11-22 18:01:12]

Addressed the issue, also used GetString() for the JNI string conversion.

http://codereview.adblockplus.org/5668574207148032/diff/5629499534213120/jni/...
File jni/AndroidWebRequest.cpp (right):

http://codereview.adblockplus.org/5668574207148032/diff/5629499534213120/jni/...
jni/AndroidWebRequest.cpp:52: return ("Java Exception: " + message).c_str();
On 2013/11/22 17:51:03, Wladimir Palant wrote:
> You are creating a temporary std::string instance here and returning a
reference
> to its buffer - this will likely crash. You should add "Java Exception: " when
> you are initializing the message variable in the constructor, this way there
> shouldn't be any trouble.

Done.

[Wladimir Palant, 2013-11-22 18:04:34]

LGTM