Add new MouseCursor interface for setting the mouse cursor.

ppapi/thunk/ppb_mouse_lock_thunk.cc

Index: ppapi/thunk/ppb_mouse_lock_thunk.cc
diff --git a/ppapi/thunk/ppb_mouse_lock_thunk.cc b/ppapi/thunk/ppb_mouse_lock_thunk.cc
index 11d2012805498c198dba9b04fe0c23fb328c5dbd..d884ab09e554eb785ee9f922576540cf91fcbd88 100644
--- a/ppapi/thunk/ppb_mouse_lock_thunk.cc
+++ b/ppapi/thunk/ppb_mouse_lock_thunk.cc
@@ -14,14 +14,14 @@ namespace thunk {
 namespace {
 
 int32_t LockMouse(PP_Instance instance, PP_CompletionCallback callback) {
-  EnterFunction<PPB_Instance_FunctionAPI> enter(instance, callback, true);
+  EnterInstance enter(instance, callback);
   if (enter.failed())
     return enter.retval();
   return enter.SetResult(enter.functions()->LockMouse(instance, callback));
 }
 
 void UnlockMouse(PP_Instance instance) {
-  EnterFunction<PPB_Instance_FunctionAPI> enter(instance, true);
+  EnterInstance enter(instance);
   if (enter.failed())
     return;
   enter.functions()->UnlockMouse(instance);