Mojo: add support for disallowing sync calls for a process.

mojo/edk/system/core.h

Index: mojo/edk/system/core.h
diff --git a/mojo/edk/system/core.h b/mojo/edk/system/core.h
index ee474cb5ab3032add4ced4323f9a215449a90965..b273a69e962c65bcbff192e3e0ad8c2b0f4cd165 100644
--- a/mojo/edk/system/core.h
+++ b/mojo/edk/system/core.h
@@ -124,6 +124,8 @@ class MOJO_SYSTEM_IMPL_EXPORT Core {
                        MojoHandleSignals signals,
                        const base::Callback<void(MojoResult)>& callback);
 
+  MojoResult SetProperty(MojoPropertyType type, const void* value);
+
   // ---------------------------------------------------------------------------
 
   // The following methods are essentially implementations of the Mojo Core
@@ -158,6 +160,7 @@ class MOJO_SYSTEM_IMPL_EXPORT Core {
                           MojoMessageHandle* message);
   MojoResult FreeMessage(MojoMessageHandle message);
   MojoResult GetMessageBuffer(MojoMessageHandle message, void** buffer);
+  MojoResult GetProperty(MojoPropertyType type, void* value);
 
   // These methods correspond to the API functions defined in
   // "mojo/public/c/system/wait_set.h":
@@ -301,6 +304,10 @@ class MOJO_SYSTEM_IMPL_EXPORT Core {
   base::Lock mapping_table_lock_;  // Protects |mapping_table_|.
   MappingTable mapping_table_;
 
+  base::Lock property_lock_;
+  // Properties that can be read using the MojoGetProperty() API.
+  bool property_sync_call_allowed_ = true;
+
   DISALLOW_COPY_AND_ASSIGN(Core);
 };