Push API: register PushMessagingServiceImpl as GCMAppHandler.

components/gcm_driver/gcm_driver.cc

Index: components/gcm_driver/gcm_driver.cc
diff --git a/components/gcm_driver/gcm_driver.cc b/components/gcm_driver/gcm_driver.cc
index 345fa97dce156622f51083e91f9a98277c68cf9d..cfe9f99eaf68a04e4b6e6573e0886fa469ed37a1 100644
--- a/components/gcm_driver/gcm_driver.cc
+++ b/components/gcm_driver/gcm_driver.cc
@@ -148,7 +148,7 @@ void GCMDriver::AddAppHandler(const std::string& app_id,
                               GCMAppHandler* handler) {
   DCHECK(!app_id.empty());
   DCHECK(handler);
-  DCHECK(app_handlers_.find(app_id) == app_handlers_.end());
+  DCHECK_EQ(app_handlers_.count(app_id), 0u);
   app_handlers_[app_id] = handler;
 }
 
@@ -158,8 +158,18 @@ void GCMDriver::RemoveAppHandler(const std::string& app_id) {
 }
 
 GCMAppHandler* GCMDriver::GetAppHandler(const std::string& app_id) {
+  // Look for exact match.
   GCMAppHandlerMap::const_iterator iter = app_handlers_.find(app_id);
-  return iter == app_handlers_.end() ? &default_app_handler_ : iter->second;
+  if (iter != app_handlers_.end())
+    return iter->second;
+
+  // Ask the handlers whether they know how to handle it.
+  for (iter = app_handlers_.begin(); iter != app_handlers_.end(); ++iter) {
+    if (iter->second->CanHandle(app_id))
+      return iter->second;
+  }
+
+  return &default_app_handler_;
 }
 
 bool GCMDriver::HasRegisterCallback(const std::string& app_id) {