Issue 242 - Use user style sheets on Chromium

lib/cssInjection.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 14 matching lines @@
 const {checkWhitelisted} = require("whitelisting");
 const {extractHostFromFrame} = require("url");
 const {port} = require("messaging");
 const devtools = require("devtools");
 const info = require("info");
 
 // Chromium's support for tabs.removeCSS is still a work in progress and the
 // API is likely to be different from Firefox's; for now we just don't use it
 // at all, even if it's available.
 // See https://crbug.com/608854
-const styleSheetRemovalSupported = "removeCSS" in browser.tabs &&
-                                   info.platform == "gecko";

[Sebastian Noack, 2018/01/31 14:30:05]

tabs.removeCSS() was added in Firefox 49. The oldest version we still support is
Firefox 51. So the check for info.platform should be sufficient.

[Manish Jethani, 2018/02/01 08:05:07]

Done.

+const styleSheetRemovalSupported = info.platform == "gecko";
 
 const selectorGroupSize = 1024;
 
 let userStyleSheetsSupported = true;
 
 function* splitSelectors(selectors)
 {
   // Chromium's Blink engine supports only up to 8,192 simple selectors, and
   // even fewer compound selectors, in a rule. The exact number of selectors
   // that would work depends on their sizes (e.g. "#foo .bar" has a size of 2).
@@ skipping 27 matching lines @@
     browser.tabs.insertCSS(tabId, {
       code: styleSheet,
       cssOrigin: "user",
       frameId,
       matchAboutBlank: true,
       runAt: "document_start"
     });
   }
   catch (error)
   {
-    if (/\bError processing cssOrigin\b/.test(error.message) == -1)

[Sebastian Noack, 2018/01/31 14:30:05]

I wonder how safe the assumption is that this will match any error indicating
unsupported cssOrigin on all versions of Chromium and Firefox. On the other
hand, without this check we would just fall back to content script injected
author style sheets, as well in the theoretical scenario where insertCSS() might
fail for another reason. That doesn't seem too bad to me.

[Manish Jethani, 2018/02/01 08:05:07]

OK, I think we should just look for /\bcssOrigin\b/ here. We already know it's
an error, then if we know the error message contains the word "cssOrigin", and
since we've passed the value "user" to that option, we can conclude that user
style sheets are not supported. This is more general than the previous check.

Done.

[Sebastian Noack, 2018/02/01 10:32:50]

I still think, we should just remove that check all together. But it's not too
important. Let's see what Dave says.

[Manish Jethani, 2018/02/01 10:40:38]

Yeah I'm cool with just removing the check too. If it fails, it fails, then the
reason for failure doesn't matter. We lose the actual error but that's OK.

-      throw error;
-
     userStyleSheetsSupported = false;
   }
 
   return userStyleSheetsSupported;
 }
 
 function removeStyleSheet(tabId, frameId, styleSheet)
 {
   if (!styleSheetRemovalSupported)
     return;
@@ skipping 80 matching lines @@
     response.inlineEmulated = true;
 
   return response;
 });
 
 port.on("elemhide.injectSelectors", (message, sender) =>
 {
   updateFrameStyles(sender.page.id, sender.frame.id, message.selectors,
                     message.groupName);
 });