fix(launcher): sigkill after sigint if not dead

In some cases chrome on linux does not die when it receives a sigint
signal. So after a sigint is sent wait 2 more seconds and issue a
sigkill if the process is still running.

lib/launchers/Base.js

@@ -18,10 +18,12 @@ var BaseBrowser = function(id, emitter, captureTimeout, retryLimit) {
   var capturingUrl;
   var exitCallback = function() {};
 
+  this.killTimeout = 2000;
   this.id = id;
   this.state = null;
   this._tempDir = path.normalize((env.TMPDIR || env.TMP || env.TEMP || '/tmp') + '/karma-' +
       id.toString());
+  this.exitCallbacks = [];
 
 
   this.start = function(url) {
@@ -60,18 +62,31 @@ var BaseBrowser = function(id, emitter, captureTimeout, retryLimit) {
 
   this.kill = function(callback) {
     exitCallback = callback || function() {};
-
+    
     log.debug('Killing %s', self.name);
-
-    if (self.state !== FINISHED) {
+    if (self.state === FINISHED) {
+      process.nextTick(exitCallback);
+    } else if (self.state === BEING_KILLED) {
+      this.exitCallbacks.push(exitCallback);
+    } else {
       self.state = BEING_KILLED;
       self._process.kill();
-    } else {
-      process.nextTick(exitCallback);
+      this.exitCallbacks.push(exitCallback);
+      setTimeout(self._onKillTimeout, self.killTimeout);
     }
   };
 
 
+  this._onKillTimeout = function() {
+    if (self.state !== BEING_KILLED) {
+      return;
+    }
+
+    log.warn('%s was not killed in %d ms, sending SIGKILL.', self.name, self.killTimeout);
+
+    self._process.kill('SIGKILL');
+  };
+
   this._onTimeout = function() {
     if (self.state !== BEING_CAPTURED) {
       return;
@@ -169,6 +184,10 @@ var BaseBrowser = function(id, emitter, captureTimeout, retryLimit) {
     }
 
     self.state = FINISHED;
+    self.exitCallbacks.forEach(function(exitCallback) {
+      exitCallback();
+    });
+    self.exitCallbacks = [];
     self._cleanUpTmp(exitCallback);
   };