Bug 1584031 - Add a pref to put data URIs in their own process when using fission. r=kmag

Differential Revision: https://phabricator.services.mozilla.com/D53894

--HG--
extra : moz-landing-system : lando

modules/libpref/init/all.js

@@ -2705,6 +2705,10 @@ pref("browser.tabs.remote.autostart", false);
 // of file:// URIs.
 pref("browser.tabs.remote.separateFileUriProcess", true);
 
+// Pref to control whether we put all data: uri's in the default
+// web process when running with fission.
+pref("browser.tabs.remote.dataUriInDefaultWebProcess", false);
+
 // Pref that enables top level web content pages that are opened from file://
 // URI pages to run in the file content process.
 // This has been added in case breaking any window references between these

toolkit/modules/E10SUtils.jsm

@@ -23,6 +23,12 @@ XPCOMUtils.defineLazyPreferenceGetter(
   "browser.tabs.remote.separateFileUriProcess",
   false
 );
+XPCOMUtils.defineLazyPreferenceGetter(
+  this,
+  "useSeparateDataUriProcess",
+  "browser.tabs.remote.dataUriInDefaultWebProcess",
+  false
+);
 XPCOMUtils.defineLazyPreferenceGetter(
   this,
   "allowLinkedWebInFileUriProcess",
@@ -535,11 +541,17 @@ var E10SUtils = {
       throw Cr.NS_ERROR_UNEXPECTED;
     }
 
-    // Null principals can be loaded in any remote process.
+    // Null principals can be loaded in any remote process, but when
+    // using fission we add the option to force them into the default
+    // web process for better test coverage.
     if (aPrincipal.isNullPrincipal) {
-      return aPreferredRemoteType == NOT_REMOTE
-        ? DEFAULT_REMOTE_TYPE
-        : aPreferredRemoteType;
+      if (
+        (aRemoteSubframes && useSeparateDataUriProcess) ||
+        aPreferredRemoteType == NOT_REMOTE
+      ) {
+        return WEB_REMOTE_TYPE;
+      }
+      return aPreferredRemoteType;
     }
 
     // We might care about the currently loaded URI. Pull it out of our current
@@ -759,7 +771,9 @@ var E10SUtils = {
     // http(s) uri, so make sure we switch if we're currently in that process.
     if (
       (useRemoteSubframes || useHttpResponseProcessSelection) &&
-      (aURI.scheme == "http" || aURI.scheme == "https") &&
+      (aURI.scheme == "http" ||
+        aURI.scheme == "https" ||
+        aURI.scheme == "data") &&
       Services.appinfo.remoteType != NOT_REMOTE
     ) {
       return true;