HeadlessWebContents:Observer to observe render process exit status

headless/lib/browser/headless_devtools_client_impl.cc

Index: headless/lib/browser/headless_devtools_client_impl.cc
diff --git a/headless/lib/browser/headless_devtools_client_impl.cc b/headless/lib/browser/headless_devtools_client_impl.cc
index 833b9dc49afb1d85c386d64865b20448c98cfa57..010d3d113da09e661e20e5a558a5b0d0e8064494 100644
--- a/headless/lib/browser/headless_devtools_client_impl.cc
+++ b/headless/lib/browser/headless_devtools_client_impl.cc
@@ -32,6 +32,7 @@ HeadlessDevToolsClientImpl* HeadlessDevToolsClientImpl::From(
 HeadlessDevToolsClientImpl::HeadlessDevToolsClientImpl()
     : agent_host_(nullptr),
       next_message_id_(0),
+      renderer_crashed_(false),
       accessibility_domain_(this),
       animation_domain_(this),
       application_cache_domain_(this),
@@ -78,7 +79,8 @@ void HeadlessDevToolsClientImpl::AttachToHost(
 void HeadlessDevToolsClientImpl::DetachFromHost(
     content::DevToolsAgentHost* agent_host) {
   DCHECK_EQ(agent_host_, agent_host);
-  agent_host_->DetachClient(this);
+  if (!renderer_crashed_)
+    agent_host_->DetachClient(this);
   agent_host_ = nullptr;
   pending_messages_.clear();
 }
@@ -133,6 +135,13 @@ bool HeadlessDevToolsClientImpl::DispatchEvent(
     return false;
   EventHandlerMap::const_iterator it = event_handlers_.find(method);
   if (it == event_handlers_.end()) {
+    // Silently swallow errors related to the target crashing. This can be
+    // observed via HeadlessWebContents::Observer::RenderProcessExited.
+    if (method == "Inspector.targetCrashed") {

[Sami, 2016/11/18 18:37:22]

Shouldn't we still emit this event in Headless Shell / chrome --headless?

Does the C++ notification give us something this event doesn't? I'm wondering
whether we should instead extend this event to do what we need?

[alex clarke (OOO till 29th), 2016/11/21 10:44:01]

Hmm so we do actually have an inspector domain - I hadn't appreciated that. 
Suggests that this bit of code is a mistake.

The C++ API does give us the base::TerminationStatus and platform specific exit
code.  Those might be useful still.

+      renderer_crashed_ = true;
+      return true;
+    }
+
     NOTREACHED() << "Unknown event: " << method;
     return false;
   }
@@ -292,6 +301,8 @@ template <typename CallbackType>
 void HeadlessDevToolsClientImpl::FinalizeAndSendMessage(
     base::DictionaryValue* message,
     CallbackType callback) {
+  if (renderer_crashed_)
+    return;
   DCHECK(agent_host_);
   int id = next_message_id_++;
   message->SetInteger("id", id);