Undoing revert, cl is not the cause of gcm crash on canary.

components/copresence/public/copresence_delegate.h

Index: components/copresence/public/copresence_delegate.h
diff --git a/components/copresence/public/copresence_delegate.h b/components/copresence/public/copresence_delegate.h
index b8a01bf1377d822430f27dc32a8137347cfda46b..e138d663516b10d021b4e96a0ea1e92c26f02a41 100644
--- a/components/copresence/public/copresence_delegate.h
+++ b/components/copresence/public/copresence_delegate.h
@@ -10,6 +10,10 @@
 
 #include "base/callback_forward.h"
 
+namespace gcm {
+class GCMDriver;
+}
+
 namespace net {
 class URLRequestContextGetter;
 }
@@ -49,6 +53,10 @@ class CopresenceDelegate {
 
   // Thw WhispernetClient must outlive the CopresenceManager.
   virtual WhispernetClient* GetWhispernetClient() = 0;
+
+  // Clients may optionally provide a GCMDriver to receive messages from.
+  // If no driver is available, this can return null.
+  virtual gcm::GCMDriver* GetGCMDriver() = 0;
 };
 
 }  // namespace copresence