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

ppapi/c/private/ppb_nacl_private.h

Index: ppapi/c/private/ppb_nacl_private.h
diff --git a/ppapi/c/private/ppb_nacl_private.h b/ppapi/c/private/ppb_nacl_private.h
index 9648831f6155942647901f32fac012308c968d7e..9e54ebf63edb8f33de59805177e02b3d7069a701 100644
--- a/ppapi/c/private/ppb_nacl_private.h
+++ b/ppapi/c/private/ppb_nacl_private.h
@@ -3,7 +3,7 @@
  * found in the LICENSE file.
  */
 
-/* From private/ppb_nacl_private.idl modified Mon Jul 15 09:19:33 2013. */
+/* From private/ppb_nacl_private.idl modified Fri Jul 19 09:51:16 2013. */
 
 #ifndef PPAPI_C_PRIVATE_PPB_NACL_PRIVATE_H_
 #define PPAPI_C_PRIVATE_PPB_NACL_PRIVATE_H_
@@ -114,10 +114,15 @@ struct PPB_NaCl_Private_1_0 {
                                    PP_FileHandle* target_handle,
                                    uint32_t desired_access,
                                    uint32_t options);
+  /* Check if PNaCl is installed and attempt to install if necessary.
+   * Callback is called when the check is done and PNaCl is already installed,
+   * or after an on-demand install is attempted. Called back with PP_OK is
+   * PNaCl is available. Called back with an error otherwise.
+   */
+  int32_t (*EnsurePnaclInstalled)(PP_Instance instance,
+                                  struct PP_CompletionCallback callback);
   /* Returns a read-only file descriptor of a file rooted in the Pnacl
    * component directory, or an invalid handle on failure.
-   * Do we want this to take a completion callback and be async, or
-   * could we make this happen on another thread?
    */
   PP_FileHandle (*GetReadonlyPnaclFd)(const char* filename);
   /* This creates a temporary file that will be deleted by the time