Make array allocation stub shared between isolates.

runtime/vm/debugger_x64.cc

Index: runtime/vm/debugger_x64.cc
diff --git a/runtime/vm/debugger_x64.cc b/runtime/vm/debugger_x64.cc
index 39b1ac115c4d6394810ac82f55521e1b1fb18a79..c3d2495c35e87b609b7ce16e371df3e11b3c64b6 100644
--- a/runtime/vm/debugger_x64.cc
+++ b/runtime/vm/debugger_x64.cc
@@ -22,15 +22,14 @@ uword CodeBreakpoint::OrigStubAddress() const {
 
 void CodeBreakpoint::PatchCode() {
   ASSERT(!is_enabled_);
-  StubCode* stub_code = Isolate::Current()->stub_code();
   uword stub_target = 0;
   switch (breakpoint_kind_) {
     case RawPcDescriptors::kIcCall:
     case RawPcDescriptors::kUnoptStaticCall:
-      stub_target = stub_code->ICCallBreakpointEntryPoint();
+      stub_target = StubCode::ICCallBreakpointEntryPoint();
       break;
     case RawPcDescriptors::kRuntimeCall:
-      stub_target = stub_code->RuntimeCallBreakpointEntryPoint();
+      stub_target = StubCode::RuntimeCallBreakpointEntryPoint();
       break;
     default:
       UNREACHABLE();