Make array allocation stub shared between isolates.

runtime/vm/assembler_arm.h

Index: runtime/vm/assembler_arm.h
diff --git a/runtime/vm/assembler_arm.h b/runtime/vm/assembler_arm.h
index 70dd9ad5f0b2b0c7f99fb16f1e87868e64970711..ad1cef1ca055be81e00b4d73dfbbd7cb0a8d0585 100644
--- a/runtime/vm/assembler_arm.h
+++ b/runtime/vm/assembler_arm.h
@@ -938,7 +938,8 @@ class Assembler : public ValueObject {
   // which will allocate in the runtime where tracing occurs.
   void MaybeTraceAllocation(intptr_t cid,
                             Register temp_reg,
-                            Label* trace);
+                            Label* trace,
+                            bool inline_isolate = true);
 
   // Inlined allocation of an instance of class 'cls', code has no runtime
   // calls. Jump to 'failure' if the instance cannot be allocated here.