PNaCl on-demand installs: Make a separate async IPC to check if PNaCl is installed

components/nacl/common/nacl_host_messages.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Multiply-included file, no traditional include guard.
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/process/process.h"
@@ skipping 35 matching lines @@
 // A renderer sends this to the browser process when it wants to start
 // a new instance of the Native Client process. The browser will launch
 // the process and return an IPC channel handle. This handle will only
 // be valid if the NaCl IPC proxy is enabled.
 IPC_SYNC_MESSAGE_CONTROL1_2(NaClHostMsg_LaunchNaCl,
                             nacl::NaClLaunchParams /* launch_params */,
                             nacl::NaClLaunchResult /* launch_result */,
                             std::string /* error_message */)
 
 // A renderer sends this to the browser process when it wants to
+// ensure that PNaCl is installed.
+IPC_MESSAGE_CONTROL1(NaClHostMsg_EnsurePnaclInstalled,
+                     int /* pp_instance */)
+
+// The browser replies to the renderer's request to ensure that
+// PNaCl is installed.
+IPC_MESSAGE_CONTROL2(NaClViewMsg_EnsurePnaclInstalledReply,
+                     int /* pp_instance */,
+                     bool /* success */)
+
+// A renderer sends this to the browser process when it wants to
 // open a file for from the Pnacl component directory.
 IPC_SYNC_MESSAGE_CONTROL1_1(NaClHostMsg_GetReadonlyPnaclFD,
                             std::string /* name of requested PNaCl file */,
                             IPC::PlatformFileForTransit /* output file */)
 
 // A renderer sends this to the browser process when it wants to
 // create a temporary file.
 IPC_SYNC_MESSAGE_CONTROL0_1(NaClHostMsg_NaClCreateTemporaryFile,
                             IPC::PlatformFileForTransit /* out file */)
 
@@ skipping 23 matching lines @@
                      int /* Error ID */)
 
 // A renderer sends this to the browser process when it wants to
 // open a NaCl executable file from an installed application directory.
 IPC_SYNC_MESSAGE_CONTROL2_3(NaClHostMsg_OpenNaClExecutable,
                             int /* render_view_id */,
                             GURL /* URL of NaCl executable file */,
                             IPC::PlatformFileForTransit /* output file */,
                             uint64 /* file_token_lo */,
                             uint64 /* file_token_hi */)