Fixes the 'protocol.json' fetch URL

Since Chromium version 53.0.2759.0 the file `protocol.json` has been split
(broswer and JavaScript runtime, see https://crbug.com/580337) and hence a merge
is needed.

Closes #40.

lib/devtools.js

@@ -151,34 +151,71 @@ function fetchObject(transport, options, callback) {
 }
 
 // callback(protocol)
+// XXX this function needs a proper refactor but the inconsistency of the
+// fetching process makes it useless for now
 function fetchFromChrome(options, info, callback) {
+    function explodeVersion(v) {
+        return v.split('.').map(function (x) {
+            return parseInt(x);
+        });
+    }
     // attempt to fetch the protocol directly from the Chromium repository
     // according to the current version; fallback to the hardcoded version
     //
     // Thanks to Paul Irish.
     // (see https://github.com/cyrus-and/chrome-remote-interface/issues/10#issuecomment-146032907)
-    var version = info['WebKit-Version'];
-    var match = version.match(/\s\(@(\b[0-9a-f]{5,40}\b)/);
+    var webKitVersion = info['WebKit-Version'];
+    var match = webKitVersion.match(/\s\(@(\b[0-9a-f]{5,40}\b)/);
     var hash = match[1];
     var fromChromiumDotOrg = (hash <= 202666);
-    var template = (fromChromiumDotOrg ?
-        'https://src.chromium.org/blink/trunk/Source/devtools/protocol.json?p=%s':
-        'https://chromium.googlesource.com/chromium/src/+/%s/third_party/WebKit/Source/devtools/protocol.json?format=TEXT');
-    var url = util.format(template, hash);
-    fetchObject(https, url, function (err, data) {
-        var descriptor;
-        if (!err) {
-            try {
-                // the file is served base64 encoded from googlesource.com
-                if (!fromChromiumDotOrg) {
-                    data = new Buffer(data, 'base64').toString();
+    var templates;
+    if (fromChromiumDotOrg) {
+        templates = ['https://src.chromium.org/blink/trunk/Source/devtools/protocol.json?p=%s'];
+    } else {
+        var chromeVersion = explodeVersion(info.Browser.split('/')[1]);
+        var lastChromeVersion = explodeVersion('53.0.2758.1'); // before the split (https://crbug.com/580337)
+        // according to https://www.chromium.org/developers/version-numbers
+        var beforeSplit = (chromeVersion[2] <= lastChromeVersion[2]); // patch not meaningful
+        templates = (beforeSplit ?
+            ['https://chromium.googlesource.com/chromium/src/+/%s/third_party/WebKit/Source/devtools/protocol.json?format=TEXT'] :
+            ['https://chromium.googlesource.com/chromium/src/+/%s/third_party/WebKit/Source/core/inspector/browser_protocol.json?format=TEXT',
+             'https://chromium.googlesource.com/chromium/src/+/%s/third_party/WebKit/Source/platform/v8_inspector/js_protocol.json?format=TEXT']);
+    }
+    var urls = templates.map(function (template) {
+        return util.format(template, hash);
+    });
+    var descriptors = [];
+    urls.forEach(function (url) {
+        fetchObject(https, url, function (err, data) {
+            var descriptor; // undefined == fallback
+            if (!err) {
+                try {
+                    // the file is served base64 encoded from googlesource.com
+                    if (!fromChromiumDotOrg) {
+                        data = new Buffer(data, 'base64').toString();
+                    }
+                    descriptor = JSON.parse(data);
+                } catch (_) {
+                    // fall back
                 }
-                descriptor = JSON.parse(data);
-            } catch (_) {
-                // fall back
             }
-        }
-        callback(descriptor);
+            descriptors.push(descriptor);
+            if (descriptors.length === urls.length) {
+                // all must be defined
+                if (descriptors.indexOf(undefined) !== -1) {
+                    callback();
+                    return;
+                }
+                // merge the domains
+                descriptors.forEach(function (descriptor, i) {
+                    if (i === 0) {
+                        return;
+                    }
+                    Array.prototype.push.apply(descriptors[0].domains, descriptor.domains);
+                });
+                callback(descriptors[0]);
+            }
+        });
     });
 }