Issue 242 - Use user style sheets on Chromium

lib/cssInjection.js

Index: lib/cssInjection.js
===================================================================
--- a/lib/cssInjection.js
+++ b/lib/cssInjection.js
@@ -21,19 +21,30 @@
 
 const {RegExpFilter} = require("filterClasses");
 const {ElemHide} = require("elemHide");
 const {ElemHideEmulation} = require("elemHideEmulation");
 const {checkWhitelisted} = require("whitelisting");
 const {extractHostFromFrame} = require("url");
 const {port} = require("messaging");
 const devtools = require("devtools");
+const info = require("info");
 
-const userStyleSheetsSupported = "extensionTypes" in browser &&
-                                 "CSSOrigin" in browser.extensionTypes;
+const userStyleSheetsSupported = ("extensionTypes" in browser &&
+                                  "CSSOrigin" in browser.extensionTypes) ||
+                                 (info.platform == "chromium" &&
+                                  parseInt(info.platformVersion, 10) >= 66);
+
+// 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";
+
 const selectorGroupSize = 1024;
 
 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).
   // Since we don't know the sizes of the selectors here, we simply split them
@@ -67,16 +78,19 @@
     frameId,
     matchAboutBlank: true,
     runAt: "document_start"
   });
 }
 
 function removeStyleSheet(tabId, frameId, styleSheet)
 {
+  if (!styleSheetRemovalSupported)
+    return;
+
   browser.tabs.removeCSS(tabId, {
     code: styleSheet,
     cssOrigin: "user",
     frameId,
     matchAboutBlank: true
   });
 }
 
@@ -137,16 +151,23 @@
 
   if (!inline)
     updateFrameStyles(sender.page.id, sender.frame.id, selectors);
 
   let response = {trace, inline, emulatedPatterns};
   if (trace || inline)
     response.selectors = selectors;
 
+  // If we can't remove user style sheets using tabs.removeCSS, we'll only keep
+  // adding them, which could cause problems with emulated filters as described
+  // in issue #5864. Instead, we can just ask the content script to add styles
+  // for emulated filters inline.
+  if (!styleSheetRemovalSupported)
+    response.inlineEmulated = true;
+
   return response;
 });
 
 port.on("elemhide.injectSelectors", (message, sender) =>
 {
   updateFrameStyles(sender.page.id, sender.frame.id, message.selectors,
                     message.groupName);
 });