PPAPI: Implement PPB_FileMapping on POSIX

ppapi/thunk/enter.cc

Index: ppapi/thunk/enter.cc
diff --git a/ppapi/thunk/enter.cc b/ppapi/thunk/enter.cc
index 2adc7f2d47a88239af5bcfdff77263c5363b7062..03937c9b5338b353b469fc9d92366b9f2eb1247e 100644
--- a/ppapi/thunk/enter.cc
+++ b/ppapi/thunk/enter.cc
@@ -59,7 +59,6 @@ EnterBase::EnterBase(PP_Instance instance, SingletonResourceID resource_id,
                      const PP_CompletionCallback& callback)
     : resource_(GetSingletonResource(instance, resource_id)),
       retval_(PP_OK) {
-  DCHECK(resource_ || !instance);

[teravest, 2014/01/23 21:40:58]

Why is this removed?

[dmichael (off chromium), 2014/01/24 20:02:50]

This case happens for singleton resources if you pass a bad resource, we just
had never tested that before. See the "Bad instance" part of my test; I pass
"PP_Instance(0xbadbad)", and expect to get a PP_ERROR_BADARGUMENT when the
instance can't be found. Instead, it was crashing in Debug because of this
DCHECK. (GetSingletonResource returns a NULL resource_, and instance is
non-zero).

   if (!resource_)
     retval_ = PP_ERROR_BADARGUMENT;
   callback_ = new TrackedCallback(resource_, callback);