casper: Improve common.js.

These changes prepare us for the casperjs upgrade:

    Extract init_viewport().
    Have then_log_out() do more explicit waiting.
    Add turn_off_press_enter_to_send().

frontend_tests/casper_lib/common.js

@@ -24,6 +24,11 @@ function log_in(credentials) {
     }, true /* submit form */);
 }
 
+
+exports.init_viewport = function () {
+    casper.options.viewportSize = {width: 1280, height: 1024};
+};
+
 exports.initialize_casper = function (viewport) {
     if (casper.zulip_initialized !== undefined) {
         return;
@@ -32,9 +37,6 @@ exports.initialize_casper = function (viewport) {
     // These initialization steps will fail if they run before
     // casper.start has been called.
 
-    // Set default viewport size to something reasonable
-    casper.page.viewportSize = viewport || {width: 1280, height: 1024};
-
     // Fail if we get a JavaScript error in the page's context.
     // Based on the example at http://phantomjs.org/release-1.5.html
     //
@@ -90,6 +92,7 @@ exports.start_and_log_in = function (credentials, viewport) {
     } else {
         log_in_url = "http://localhost:9981/accounts/login";
     }
+    exports.init_viewport();
     casper.start(log_in_url, function () {
         exports.initialize_casper(viewport);
         log_in(credentials);
@@ -97,11 +100,22 @@ exports.start_and_log_in = function (credentials, viewport) {
 };
 
 exports.then_log_out = function () {
-    casper.then(function () {
+    var menu_selector = '#settings-dropdown';
-        casper.test.info('Logging out');
+    var logout_selector = 'li[title="Log out"] a';
-        casper.click('li[title="Log out"] a');
-    });
 
+    casper.waitUntilVisible(menu_selector, function () {
+        casper.click(menu_selector);
+
+        casper.waitUntilVisible(logout_selector, function () {
+            casper.test.info('Logging out');
+            casper.click(logout_selector);
+
+            casper.then(function () {
+                casper.test.assertUrlMatch(/accounts\/login\/$/);
+            });
+        });
+
+    });
     casper.waitForSelector(".login-page-header", function () {
         casper.test.info("Logged out");
     });
@@ -166,6 +180,19 @@ exports.wait_for_message_actually_sent = function () {
     });
 };
 
+exports.turn_off_press_enter_to_send = function () {
+    var enter_send_selector = '#enter_sends';
+    casper.waitForSelector(enter_send_selector);
+
+    var is_checked = casper.evaluate(function (enter_send_selector) {
+        return document.querySelector(enter_send_selector).checked;
+    }, enter_send_selector);
+
+    if (is_checked) {
+        casper.click(enter_send_selector);
+    }
+};
+
 // Wait for any previous send to finish, then send a message.
 exports.then_send_message = function (type, params) {
     casper.then(function () {
@@ -182,7 +209,12 @@ exports.then_send_message = function (type, params) {
             casper.test.assertTrue(false, "send_message got valid message type");
         }
         casper.fill('form[action^="/json/messages"]', params);
-        casper.click('#compose-send-button');
+
+        exports.turn_off_press_enter_to_send();
+
+        casper.then(function () {
+            casper.click('#compose-send-button');
+        });
     });
 
     casper.then(function () {

frontend_tests/casper_tests/01-login.js

@@ -8,6 +8,7 @@ if (REALMS_HAVE_SUBDOMAINS) {
     realm_url = "http://localhost:9981/";
 }
 // Start of test script.
+common.init_viewport();
 casper.start(realm_url, common.initialize_casper);
 
 casper.then(function () {