Bug 1713619 - ESR 115: Exempt chrome/resource principals from canvas...

Bug 1713619 - ESR 115: Exempt chrome/resource principals from canvas randomization/placeholders. r=lsalzman a=pascalc

Differential Revision: https://phabricator.services.mozilla.com/D197580

dom/canvas/CanvasUtils.cpp

@@ -110,6 +110,11 @@ bool IsImageExtractionAllowed(dom::Document* aDocument, JSContext* aCx,
     return true;
   }
 
+  // Allow chrome: and resource: (this especially includes PDF.js)
+  if (subjectPrincipal.SchemeIs("chrome") || subjectPrincipal.SchemeIs("resource")) {
+    return true;
+  }
+
   // Allow extension principals.
   auto* principal = BasePrincipal::Cast(&subjectPrincipal);
   if (principal->AddonPolicy() || principal->ContentScriptAddonPolicy()) {
@@ -126,13 +131,6 @@ bool IsImageExtractionAllowed(dom::Document* aDocument, JSContext* aCx,
     return true;
   }
 
-  // Don't show canvas prompt for PDF.js
-  JS::AutoFilename scriptFile;
-  if (JS::DescribeScriptedCaller(aCx, &scriptFile) && scriptFile.get() &&
-      strcmp(scriptFile.get(), "resource://pdf.js/build/pdf.js") == 0) {
-    return true;
-  }
-
   // -------------------------------------------------------------------
   // Possibly block third parties