Gets presentation ID from route ID upon route creation, and overrides previous presentation ID with…

content/browser/presentation/presentation_service_impl.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/presentation/presentation_service_impl.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "content/browser/presentation/presentation_type_converters.h"
@@ skipping 439 matching lines @@
 
   on_session_messages_callback_.reset(new SessionMessagesCallback(callback));
   delegate_->ListenForSessionMessages(
       render_process_id_, render_frame_id_,
       base::Bind(&PresentationServiceImpl::OnSessionMessages,
                  weak_factory_.GetWeakPtr()));
 }
 
 void PresentationServiceImpl::OnSessionMessages(
     scoped_ptr<ScopedVector<PresentationSessionMessage>> messages) {
-  DCHECK(messages.get() && !messages->empty());
   if (!on_session_messages_callback_.get()) {
     // The Reset method of this class was invoked.
     return;
   }
 
-  mojo::Array<presentation::SessionMessagePtr> mojoMessages(messages->size());
-  for (size_t i = 0; i < messages->size(); ++i) {
-    mojoMessages[i] = ToMojoSessionMessage((*messages)[i]);
+  if (!messages.get() || messages->empty()) {
+    // Error handling. Session is either closed or in error state.
+    on_session_messages_callback_->Run(
+        mojo::Array<presentation::SessionMessagePtr>());
+  } else {
+    mojo::Array<presentation::SessionMessagePtr> mojoMessages(messages->size());
+    for (size_t i = 0; i < messages->size(); ++i) {

[Kevin M, 2015/06/25 22:51:56]

for (const auto& next_message : *messages)

[haibinlu, 2015/06/26 00:12:00]

with "for", I can not reverse the array size. 

mojo::Array<presentation::SessionMessagePtr> mojoMessages(0); 
for(const auto& message : *messages)
      mojoMessages.push_back(ToMojoSessionMessage(message));
   

+      mojoMessages[i] = ToMojoSessionMessage((*messages)[i]);
+    }
+    on_session_messages_callback_->Run(mojoMessages.Pass());
   }
 
-  on_session_messages_callback_->Run(mojoMessages.Pass());
   on_session_messages_callback_.reset();
 }
 
 void PresentationServiceImpl::DidNavigateAnyFrame(
     content::RenderFrameHost* render_frame_host,
     const content::LoadCommittedDetails& details,
     const content::FrameNavigateParams& params) {
   DVLOG(2) << "PresentationServiceImpl::DidNavigateAnyFrame";
   if (!FrameMatches(render_frame_host))
     return;
@@ skipping 151 matching lines @@
 void PresentationServiceImpl::DefaultSessionStartContext::Reset() {
   ScopedVector<DefaultSessionMojoCallback> callbacks;
   callbacks.swap(callbacks_);
   for (const auto& callback : callbacks)
     callback->Run(presentation::PresentationSessionInfoPtr());
   session_.reset();
 }
 
 }  // namespace content