Remove the password prompt input type hack

The browsers have become smarter and made this hack no longer
functional. Since this is now enforced by practically all browsers,
there is nothing more we can do about this. It is up to the user to
serve the viewer over HTTPS or deal with the warning.

Note that this is in no way specific for PDF.js. Any site with password
inputs served over HTTP has this problem right now. This hack was
provided as a convenience for the users, but nothing more than that.

web/password_prompt.js

@@ -60,7 +60,6 @@ class PasswordPrompt {
 
   open() {
     OverlayManager.open(this.overlayName).then(() => {
-      this.input.type = 'password';
       this.input.focus();
 
       var promptString = mozL10n.get('password_label', null,
@@ -78,7 +77,6 @@ class PasswordPrompt {
   close() {
     OverlayManager.close(this.overlayName).then(() => {
       this.input.value = '';
-      this.input.type = '';
     });
   }
 

web/viewer.html

@@ -307,8 +307,7 @@ See https://github.com/adobe-type-tools/cmap-resources
               <p id="passwordText" data-l10n-id="password_label">Enter the password to open this PDF file:</p>
             </div>
             <div class="row">
-              <!-- The type="password" attribute is set via script, to prevent warnings in Firefox for all http:// documents. -->
-              <input id="password" class="toolbarField">
+              <input type="password" id="password" class="toolbarField">
             </div>
             <div class="buttonRow">
               <button id="passwordCancel" class="overlayButton"><span data-l10n-id="password_cancel">Cancel</span></button>