Simplify VirtualMemory by removing unused ReserveAligned method.

runtime/vm/virtual_memory_macos.cc

Index: runtime/vm/virtual_memory_macos.cc
===================================================================
--- runtime/vm/virtual_memory_macos.cc	(revision 41000)
+++ runtime/vm/virtual_memory_macos.cc	(working copy)
@@ -28,7 +28,7 @@
 }
 
 
-VirtualMemory* VirtualMemory::Reserve(intptr_t size) {
+VirtualMemory* VirtualMemory::ReserveInternal(intptr_t size) {
   ASSERT((size & (PageSize() - 1)) == 0);
   void* address = mmap(NULL, size, PROT_NONE,
                        MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
@@ -37,7 +37,7 @@
     return NULL;
   }
   MemoryRegion region(address, size);
-  return new VirtualMemory(region, NULL);
+  return new VirtualMemory(region);
 }
 
 
@@ -53,12 +53,13 @@
 
 
 VirtualMemory::~VirtualMemory() {
-  unmap(address(), size());
+  unmap(address(), reserved_size_);
 }
 
 
 void VirtualMemory::FreeSubSegment(void* address, intptr_t size) {
   unmap(address, size);
+  return true;
 }