[Extensions] Add more bindings access checks

BUG=598165

Review URL: https://codereview.chromium.org/1854983002

Cr-Commit-Position: refs/heads/master@{#385282}
 PageCaptureCustomBindings::PageCaptureCustomBindings(ScriptContext* context)
     : ObjectBackedNativeHandler(context) {
  RouteFunction("CreateBlob", "pageCapture",
                base::Bind(&PageCaptureCustomBindings::CreateBlob,
                           base::Unretained(this)));
  RouteFunction("SendResponseAck", "pageCapture",
                base::Bind(&PageCaptureCustomBindings::SendResponseAck,
                           base::Unretained(this)));
 }

 PageCaptureCustomBindings::PageCaptureCustomBindings(ScriptContext* context)
     : ObjectBackedNativeHandler(context) {
  RouteFunction("CreateBlob",
      base::Bind(&PageCaptureCustomBindings::CreateBlob,
                 base::Unretained(this)));
  RouteFunction("SendResponseAck",
      base::Bind(&PageCaptureCustomBindings::SendResponseAck,
                 base::Unretained(this)));
 }
