PPAPI: Add PluginPrivateFileSystem

ppapi/proxy/isolated_file_system_private_resource.cc

Index: ppapi/proxy/isolated_file_system_private_resource.cc
diff --git a/ppapi/proxy/isolated_file_system_private_resource.cc b/ppapi/proxy/isolated_file_system_private_resource.cc
index 756bdb7bd6c1a5eacb890853dcfc094255a2e510..b4827de40e7c7b35a840cf30e6ce5045842d876f 100644
--- a/ppapi/proxy/isolated_file_system_private_resource.cc
+++ b/ppapi/proxy/isolated_file_system_private_resource.cc
@@ -47,6 +47,14 @@ int32_t IsolatedFileSystemPrivateResource::Open(
   if (!file_system_resource)
     return PP_ERROR_BADARGUMENT;
 
+#ifndef OS_CHROMEOS
+  // PluginPrivate filesystem is supported only on ChromeOS.

[dmichael (off chromium), 2013/11/15 17:42:44]

Thanks. I think we want to actually check this on the host side, though.
Messages from the plugin can be forged (especially in NaCl). I don't think
there's a security concern with this particular API, but we shouldn't ever trust
the plugin code.

BTW: Does the backend stuff make any assumptions about it being ChromeOS only?
Justin and I were just talking, and we could arguably make this a stable API
some day. It won't be as useful on other platforms, but we still *could* do it
if the backend supports it.

[nhiroki, 2013/11/18 11:21:17]

Good to know. I considered this closely, and I think the backend does not make
any assumptions about ChromeOS, so we can remove this check (and removed).

+  if (type == PP_ISOLATEDFILESYSTEMTYPE_PRIVATE_PLUGINPRIVATE) {
+    LOG(WARNING) << "PluginPrivate filesystem is not supported.";
+    return PP_ERROR_NOTSUPPORTED;
+  }
+#endif
+
   Call<PpapiPluginMsg_IsolatedFileSystem_BrowserOpenReply>(BROWSER,
       PpapiHostMsg_IsolatedFileSystem_BrowserOpen(type),
       base::Bind(&IsolatedFileSystemPrivateResource::OnBrowserOpenComplete,