VM: Optimized context allocation on all platforms.

runtime/vm/assembler_mips.h

Index: runtime/vm/assembler_mips.h
===================================================================
--- runtime/vm/assembler_mips.h	(revision 38897)
+++ runtime/vm/assembler_mips.h	(working copy)
@@ -47,7 +47,7 @@
 
 class Address : public ValueObject {
  public:
-  Address(Register base, int32_t offset = 0)
+  explicit Address(Register base, int32_t offset = 0)
       : ValueObject(), base_(base), offset_(offset) { }
 
   Address(const Address& other)
@@ -214,6 +214,14 @@
                    Register instance_reg,
                    Register temp_reg);
 
+  void TryAllocateArray(intptr_t cid,
+                        intptr_t instance_size,
+                        Label* failure,
+                        Register instance,
+                        Register end_address,
+                        Register temp1,
+                        Register temp2);
+
   // Debugging and bringup support.
   void Stop(const char* message);