Make mojo_system static and mojo_system_impl a component, never use both

mojo/system/mapping_table.h

Index: mojo/system/mapping_table.h
diff --git a/mojo/system/mapping_table.h b/mojo/system/mapping_table.h
index bbae097afcef96566e47e33847524862108593b4..1b148904f5c8a1b6c59bc653dbef49e08b90300a 100644
--- a/mojo/system/mapping_table.h
+++ b/mojo/system/mapping_table.h
@@ -18,20 +18,19 @@
 namespace mojo {
 namespace system {
 
-class CoreImpl;
+class Core;
 class RawSharedBufferMapping;
 
 // Test-only function (defined/used in embedder/test_embedder.cc). Declared here
 // so it can be friended.
 namespace internal {
-bool ShutdownCheckNoLeaks(CoreImpl*);
+bool ShutdownCheckNoLeaks(Core*);
 }
 
-// This class provides the (global) table of memory mappings (owned by
-// |CoreImpl|), which maps mapping base addresses to
-// |RawSharedBuffer::Mapping|s.
+// This class provides the (global) table of memory mappings (owned by |Core|),
+// which maps mapping base addresses to |RawSharedBuffer::Mapping|s.
 //
-// This class is NOT thread-safe; locking is left to |CoreImpl|.
+// This class is NOT thread-safe; locking is left to |Core|.
 class MOJO_SYSTEM_IMPL_EXPORT MappingTable {
  public:
   MappingTable();
@@ -43,7 +42,7 @@ class MOJO_SYSTEM_IMPL_EXPORT MappingTable {
   MojoResult RemoveMapping(void* address);
 
  private:
-  friend bool internal::ShutdownCheckNoLeaks(CoreImpl*);
+  friend bool internal::ShutdownCheckNoLeaks(Core*);
 
   typedef base::hash_map<uintptr_t, RawSharedBufferMapping*>
       AddressToMappingMap;