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

components/nacl/common/nacl_browser_delegate.h

Index: components/nacl/common/nacl_browser_delegate.h
diff --git a/components/nacl/common/nacl_browser_delegate.h b/components/nacl/common/nacl_browser_delegate.h
index 60528918f2c30cad841159d40ac5038833e81b62..6cff071716e1c2ce12dc1ecdd64b9cfb2ede868a 100644
--- a/components/nacl/common/nacl_browser_delegate.h
+++ b/components/nacl/common/nacl_browser_delegate.h
@@ -7,6 +7,8 @@
 
 #include <string>
 
+#include "base/callback_forward.h"
+
 namespace base {
 class FilePath;
 }
@@ -53,6 +55,12 @@ class NaClBrowserDelegate {
   // Returns a HostFactory that hides the details of its embedder.
   virtual ppapi::host::HostFactory* CreatePpapiHostFactory(
       content::BrowserPpapiHost* ppapi_host) = 0;
+  // Install PNaCl if this operation is supported. On success, the |installed|
+  // callback should be called with true, and on failure (or not supported),
+  // the |installed| callback should be called with false.
+  // TODO(jvoung): Add the progress callback as well.
+  virtual void TryInstallPnacl(
+      const base::Callback<void(bool)>& installed) = 0;
 };
 
 #endif  // COMPONENTS_NACL_COMMON_NACL_BROWSER_DELEGATE_H_