Add support for object pool

runtime/vm/assembler_mips.h

Index: runtime/vm/assembler_mips.h
===================================================================
--- runtime/vm/assembler_mips.h	(revision 18597)
+++ runtime/vm/assembler_mips.h	(working copy)
@@ -115,7 +115,11 @@
 
 class Assembler : public ValueObject {
  public:
-  Assembler() { UNIMPLEMENTED(); }
+  Assembler()
+      : buffer_(),
+        object_pool_(GrowableObjectArray::Handle()),
+        prologue_offset_(-1),
+        comments_() { }
   ~Assembler() { }
 
   void PopRegister(Register r) {
@@ -139,6 +143,10 @@
     UNIMPLEMENTED();
     return *pointer_offsets_;
   }
+  const GrowableObjectArray& object_pool() const {
+    UNIMPLEMENTED();
+    return object_pool_;
+  }
   void FinalizeInstructions(const MemoryRegion& region) {
     UNIMPLEMENTED();
   }
@@ -169,6 +177,7 @@
 
  private:
   AssemblerBuffer buffer_;
+  GrowableObjectArray& object_pool_;  // Objects and patchable jump targets.
   ZoneGrowableArray<int>* pointer_offsets_;
   int prologue_offset_;