Replace browser conditions by preprocessed conditions

The extension used to rely on the isFirefox method to check whether the
browser is Firefox or Chromium-based. This CL removes this function and
replaces the conditions based in this function by conditions which are
pre-processed at compile time.

Change-Id: Id7280e6c8fb3dfd3fabbc05339ef3791822aa6ac
diff --git a/src/options/optionsCommon.js b/src/options/optionsCommon.js
index bd40416..863232d 100644
--- a/src/options/optionsCommon.js
+++ b/src/options/optionsCommon.js
@@ -1,4 +1,4 @@
-import {getExtVersion, isFirefox, isReleaseVersion} from '../common/extUtils.js';
+import {getExtVersion, isReleaseVersion} from '../common/extUtils.js';
 import {ensureOptPermissions, grantedOptPermissions, missingPermissions} from '../common/optionsPermissions.js';
 import {cleanUpOptions, optionsPrototype, specialOptions} from '../common/optionsUtils.js';
 
@@ -35,9 +35,6 @@
       case 'ccdarktheme_mode':
         return document.getElementById(opt).value || 'switch';
 
-      case 'ccdragndropfix':
-        return document.getElementById(opt).checked || false;
-
       default:
         console.warn('Unrecognized option: ' + opt);
         return undefined;
@@ -232,19 +229,6 @@
                 .appendChild(select);
             break;
 
-          // Firefox doesn't support drag and dropping bookmarks into the text
-          // editor while preserving the bookmark title.
-          case 'ccdragndropfix':
-            var showOption = !isFirefox();
-            if (showOption) {
-              document.getElementById('dragndrop-wrapper')
-                  .removeAttribute('hidden');
-
-              if (items[opt] === true)
-                document.getElementById(opt).checked = true;
-            }
-            break;
-
           default:
             console.warn('Unrecognized option: ' + opt);
             break;