Enable concurrent sweep on MIPS and ARM64.

runtime/vm/pages.cc

Index: runtime/vm/pages.cc
diff --git a/runtime/vm/pages.cc b/runtime/vm/pages.cc
index ff0fa5385a378d9f84e916bf6e48e45630285b90..af3b4a3412def171900860c8f194c5a534476faf 100644
--- a/runtime/vm/pages.cc
+++ b/runtime/vm/pages.cc
@@ -37,13 +37,8 @@ DEFINE_FLAG(bool, log_code_drop, false,
             "Emit a log message when pointers to unused code are dropped.");
 DEFINE_FLAG(bool, always_drop_code, false,
             "Always try to drop code if the function's usage counter is >= 0");
-#if defined(TARGET_ARCH_MIPS) || defined(TARGET_ARCH_ARM64)
-DEFINE_FLAG(bool, concurrent_sweep, false,
-            "Concurrent sweep for old generation.");
-#else  // TARGET_ARCH_MIPS || TARGET_ARCH_ARM64
 DEFINE_FLAG(bool, concurrent_sweep, true,
             "Concurrent sweep for old generation.");
-#endif  // TARGET_ARCH_MIPS || TARGET_ARCH_ARM64
 DEFINE_FLAG(bool, log_growth, false, "Log PageSpace growth policy decisions.");
 
 HeapPage* HeapPage::Initialize(VirtualMemory* memory, PageType type) {