Remove RenderFrameHost pointer from ChooserController.

chrome/browser/usb/usb_chooser_context.h

Index: chrome/browser/usb/usb_chooser_context.h
diff --git a/chrome/browser/usb/usb_chooser_context.h b/chrome/browser/usb/usb_chooser_context.h
index 09b009c0f0899254e0957c4b1db6d516cc2c02c5..c3ef4238e5b304cb647bc32d17fed4b1a296379a 100644
--- a/chrome/browser/usb/usb_chooser_context.h
+++ b/chrome/browser/usb/usb_chooser_context.h
@@ -49,6 +49,8 @@ class UsbChooserContext : public ChooserContextBase,
                            const GURL& embedding_origin,
                            scoped_refptr<const device::UsbDevice> device);
 
+  base::WeakPtr<UsbChooserContext> AsWeakPtr();
+
  private:
   // ChooserContextBase implementation.
   bool IsValidObject(const base::DictionaryValue& object) override;
@@ -60,6 +62,7 @@ class UsbChooserContext : public ChooserContextBase,
   std::map<std::pair<GURL, GURL>, std::set<std::string>> ephemeral_devices_;
   device::UsbService* usb_service_;
   ScopedObserver<device::UsbService, device::UsbService::Observer> observer_;
+  base::WeakPtrFactory<UsbChooserContext> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbChooserContext);
 };