Disable untrusted code mitigations on Android.

BUG=chromium:1003890

Change-Id: I3d4f51095ad33828857647be02290bfd5511399d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2919965
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Auto-Submit: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74811}

BUILD.gn

@@ -213,11 +213,8 @@ declare_args() {
 
   # Enable mitigations for executing untrusted code.
   # Disabled by default on ia32 due to conflicting requirements with embedded
-  # builtins. Enabled by default on Android since it doesn't support
-  # site-isolation in Chrome and on simulator builds which test code generation
-  # on these platforms.
-  v8_untrusted_code_mitigations =
-      v8_current_cpu != "x86" && (is_android || target_is_simulator)
+  # builtins.
+  v8_untrusted_code_mitigations = false
 
   # Enable minor mark compact.
   v8_enable_minor_mc = true