Add color enhancer as a chromium accessibility extensions.

ui/accessibility/extensions/colorenhancer/src/background.js

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * Adds filter script and css to all existing tabs.
+ *
+ * TODO(wnwen): Verify content scripts are not being injected multiple times.
+ */
+function injectContentScripts() {
+  chrome.windows.getAll({'populate': true}, function(windows) {
+    for (var i = 0; i < windows.length; i++) {
+      var tabs = windows[i].tabs;
+      for (var j = 0; j < tabs.length; j++) {
+        var url = tabs[j].url;
+        if (isDisallowedUrl(url)) {
+          continue;
+        }
+        chrome.tabs.insertCSS(
+            tabs[j].id,
+            {file: 'res/cvd.css'});
+        chrome.tabs.executeScript(
+            tabs[j].id,
+            {file: 'src/common.js'});
+        chrome.tabs.executeScript(
+            tabs[j].id,
+            {file: 'src/cvd.js'});
+      }
+    }
+  });
+}
+
+/**
+ * Updates all existing tabs with config values.
+ */
+function updateTabs() {
+  chrome.windows.getAll({'populate': true}, function(windows) {
+    for (var i = 0; i < windows.length; i++) {
+      var tabs = windows[i].tabs;
+      for (var j = 0; j < tabs.length; j++) {
+        var url = tabs[j].url;
+        if (isDisallowedUrl(url)) {
+          continue;
+        }
+        debugPrint('sending  to ' + siteFromUrl(url) + ' ' +
+            getSiteDelta(siteFromUrl(url)) + ',' +
+            getSiteSeverity(siteFromUrl(url)));
+        var msg = {
+          'delta': getSiteDelta(siteFromUrl(url)),
+          'severity': getSiteSeverity(siteFromUrl(url)),
+          'type': getDefaultType(),
+          'simulate': getDefaultSimulate()
+        };
+        chrome.tabs.sendRequest(tabs[j].id, msg);
+      }
+    }
+  });
+}
+
+/**
+ * Initial extension loading.
+ */
+(function initialize() {
+  injectContentScripts();
+  updateTabs();
+
+  chrome.extension.onRequest.addListener(
+      function(request, sender, sendResponse) {
+        if (request['init']) {
+          var delta = getDefaultDelta();
+          if (sender.tab) {
+            delta = getSiteDelta(siteFromUrl(sender.tab.url));
+          }
+
+          var severity = getDefaultSeverity();
+          if (sender.tab) {
+            severity = getSiteSeverity(siteFromUrl(sender.tab.url));
+          }
+
+          var type = getDefaultType();
+          var simulate = getDefaultSimulate();
+
+          var msg = {
+            'delta': delta,
+            'severity': severity,
+            'type': getDefaultType(),
+            'simulate': getDefaultSimulate()
+          };
+          sendResponse(msg);
+        }
+      });
+
+  document.addEventListener('storage', function(evt) {
+    updateTabs();
+  }, false);
+})();