From f342f6ce122895ab2959a45d827d022ecca9710f Mon Sep 17 00:00:00 2001
From: ownedbywuigi <ownedbywuigi@gmail.com>
Date: Sun, 29 Mar 2026 23:00:40 +0100
Subject: [PATCH] Revert one process per tab, regression in backspace handling

---
 application/basilisk/app/profile/basilisk.js |  6 ++----
 dom/ipc/ContentParent.cpp                    | 10 +---------
 toolkit/xre/nsAppRunner.cpp                  |  9 +++------
 3 files changed, 6 insertions(+), 19 deletions(-)

diff --git a/application/basilisk/app/profile/basilisk.js b/application/basilisk/app/profile/basilisk.js
index 80a7127652..c1d2cae3be 100644
--- a/application/basilisk/app/profile/basilisk.js
+++ b/application/basilisk/app/profile/basilisk.js
@@ -924,10 +924,8 @@ pref("dom.ipc.shims.enabledWarnings", false);
 pref("browser.tabs.remote.autostart", true);
 pref("browser.tabs.remote.desktopbehavior", true);
 pref("browser.tabs.remote.ignoreBlockPolicy", true);
-// -1 means automatic tab-isolation mode: try one process per tab.
-pref("dom.ipc.processCount", -1);
-// Safety ceiling used by automatic tab-isolation mode.
-pref("dom.ipc.processCount.webIsolatedMax", 64);
+// Number of web content processes used by e10s.
+pref("dom.ipc.processCount", 2);
 
 // This pref governs whether we attempt to work around problems caused by
 // plugins using OS calls to manipulate the cursor while running out-of-
diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index 8577af7b8c..6dab0bbc82 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -574,7 +574,6 @@ ContentParent::GetNewOrUsedBrowserProcess(bool aForBrowserElement,
 {
   nsTArray<ContentParent*>* contentParents;
   int32_t maxContentParents;
-  bool preferDedicatedProcess = false;
 
   // Decide which pool of content parents we are going to be pulling from based
   // on the aLargeAllocationProcess flag.
@@ -592,20 +591,13 @@ ContentParent::GetNewOrUsedBrowserProcess(bool aForBrowserElement,
     contentParents = sBrowserContentParents;
 
     maxContentParents = Preferences::GetInt("dom.ipc.processCount", 1);
-    if (maxContentParents == -1) {
-      // Automatic mode: create a dedicated content process per new tab until
-      // a safety ceiling is reached, then reuse existing processes.
-      preferDedicatedProcess = true;
-      maxContentParents = Preferences::GetInt("dom.ipc.processCount.webIsolatedMax", 64);
-    }
   }
 
   if (maxContentParents < 1) {
     maxContentParents = 1;
   }
 
-  if (!preferDedicatedProcess ||
-      contentParents->Length() >= uint32_t(maxContentParents)) {
+  if (contentParents->Length() >= uint32_t(maxContentParents)) {
     uint32_t maxSelectable = std::min(static_cast<uint32_t>(contentParents->Length()),
                                       static_cast<uint32_t>(maxContentParents));
     uint32_t startIdx = rand() % maxSelectable;
diff --git a/toolkit/xre/nsAppRunner.cpp b/toolkit/xre/nsAppRunner.cpp
index c04b8f6034..c11ca26c40 100644
--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -4203,12 +4203,6 @@ MultiprocessBlockPolicy() {
   }
   gMultiprocessBlockPolicyInitialized = true;
 
-  // Allow downstream applications to bypass legacy e10s block policies.
-  // This is evaluated at startup and requires restart to take effect.
-  if (Preferences::GetBool("browser.tabs.remote.ignoreBlockPolicy", false)) {
-    return gMultiprocessBlockPolicy;
-  }
-
   /**
    * Avoids enabling e10s if there are add-ons installed.
    */
@@ -4252,6 +4246,9 @@ MultiprocessBlockPolicy() {
     gMultiprocessBlockPolicy = kE10sDisabledForAccessibility;
   }
 #endif
+
+  // We do not support E10S, block by policy.
+  gMultiprocessBlockPolicy = kE10sForceDisabled;
   
   return gMultiprocessBlockPolicy;
 }