VM: Optimized context allocation on all platforms.

runtime/vm/assembler_x64.h

Index: runtime/vm/assembler_x64.h
===================================================================
--- runtime/vm/assembler_x64.h	(revision 38897)
+++ runtime/vm/assembler_x64.h	(working copy)
@@ -861,6 +861,9 @@
   void UpdateAllocationStatsWithSize(intptr_t cid,
                                      Register size_reg,
                                      Heap::Space space = Heap::kNew);
+  void UpdateAllocationStatsWithSize(intptr_t cid,
+                                     intptr_t instance_size,
+                                     Heap::Space space = Heap::kNew);
 
   // Inlined allocation of an instance of class 'cls', code has no runtime
   // calls. Jump to 'failure' if the instance cannot be allocated here.
@@ -874,6 +877,13 @@
                    Register instance_reg,
                    Register pp);
 
+  void TryAllocateArray(intptr_t cid,
+                        intptr_t instance_size,
+                        Label* failure,
+                        bool near_jump,
+                        Register instance,
+                        Register end_address);
+
   // Debugging and bringup support.
   void Stop(const char* message);
   void Unimplemented(const char* message);
@@ -1021,6 +1031,10 @@
                                   Register value,
                                   Label* no_update);
 
+  void ComputeCounterAddressesForCid(intptr_t cid,
+                                     Heap::Space space,
+                                     Address* count_address,
+                                     Address* size_address);
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };