Fuchsia: Platform specific calls needed to Initialize and Cleanup VM.

runtime/vm/virtual_memory.h

Index: runtime/vm/virtual_memory.h
diff --git a/runtime/vm/virtual_memory.h b/runtime/vm/virtual_memory.h
index 270d3cf8f763c4b268f09a2a714e142ee4943532..6e43cb43c61ec66edcdea6034d5fb0e0046fbea7 100644
--- a/runtime/vm/virtual_memory.h
+++ b/runtime/vm/virtual_memory.h
@@ -24,6 +24,7 @@ class VirtualMemory {
   // The reserved memory is unmapped on destruction.
   ~VirtualMemory();
 
+  int32_t handle() const { return handle_; }
   uword start() const { return region_.start(); }
   uword end() const { return region_.end(); }
   void* address() const { return region_.pointer(); }
@@ -82,9 +83,10 @@ class VirtualMemory {
 
   // This constructor is only used internally when reserving new virtual spaces.
   // It does not reserve any virtual address space on its own.
-  explicit VirtualMemory(const MemoryRegion& region) :
+  explicit VirtualMemory(const MemoryRegion& region, int32_t handle = 0) :
       region_(region.pointer(), region.size()),
       reserved_size_(region.size()),
+      handle_(handle),
       embedder_allocated_(false) { }
 
   MemoryRegion region_;
@@ -93,6 +95,8 @@ class VirtualMemory {
   // Its start coincides with region_, but its size might not, due to Truncate.
   intptr_t reserved_size_;
 
+  int32_t handle_;
+
   static uword page_size_;
 
   // True for a region provided by the embedder.