Bug 938683 - Catch and pass the error values of PR_Close() to upper layer. r=johns

dom/plugins/base/nsPluginHost.cpp

@@ -2321,7 +2321,14 @@ nsPluginHost::WritePluginInfo()
     invalidPlugins = invalidPlugins->mNext;
   }
 
-  PR_Close(fd);
+  PRStatus prrc;
+  prrc = PR_Close(fd);
+  if (prrc != PR_SUCCESS) {
+    // we should obtain a refined value based on prrc;
+    rv = NS_ERROR_FAILURE;
+    MOZ_ASSERT(false, "PR_Close() failed.");
+    return rv;
+  }
   nsCOMPtr<nsIFile> parent;
   rv = pluginReg->GetParent(getter_AddRefs(parent));
   NS_ENSURE_SUCCESS(rv, rv);
@@ -2398,7 +2405,15 @@ nsPluginHost::ReadPluginInfo()
   rv = NS_ERROR_FAILURE;
 
   int32_t bread = PR_Read(fd, registry, flen);
-  PR_Close(fd);
+
+  PRStatus prrc;
+  prrc = PR_Close(fd);
+  if (prrc != PR_SUCCESS) {
+    // Strange error: this is one of those "Should not happen" error.
+    // we may want to report something more refined than  NS_ERROR_FAILURE.
+    MOZ_ASSERT(false, "PR_Close() failed.");
+    return rv;
+  }
 
   if (flen > bread)
     return rv;