Allow devtools clients to handle slow cross-process navigations.

content/browser/devtools/render_frame_devtools_agent_host.cc

Index: content/browser/devtools/render_frame_devtools_agent_host.cc
diff --git a/content/browser/devtools/render_frame_devtools_agent_host.cc b/content/browser/devtools/render_frame_devtools_agent_host.cc
index 2ac257fbc3b88d5d9e58b8c98377a0c6bc066a28..b4223fffd7eb821e0ceaed60bab620ab4798fa79 100644
--- a/content/browser/devtools/render_frame_devtools_agent_host.cc
+++ b/content/browser/devtools/render_frame_devtools_agent_host.cc
@@ -6,8 +6,10 @@
 
 #include "base/basictypes.h"
 #include "base/command_line.h"
+#include "base/json/json_reader.h"
 #include "base/lazy_instance.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/values.h"
 #include "content/browser/child_process_security_policy_impl.h"
 #include "content/browser/devtools/devtools_frame_trace_recorder.h"
 #include "content/browser/devtools/devtools_protocol_handler.h"
@@ -99,6 +101,11 @@ class RenderFrameDevToolsAgentHost::FrameHostHolder {
   void Suspend();
   void Resume();
 
+  bool suspended() const { return suspended_; }
+  const std::string& last_loading_frame_id() const {
+    return last_loading_frame_id_;
+  }
+
  private:
   void GrantPolicy();
   void RevokePolicy();
@@ -113,6 +120,7 @@ class RenderFrameDevToolsAgentHost::FrameHostHolder {
   std::vector<std::pair<int, std::string>> pending_messages_;
   // <call_id> -> <session_id, message>
   std::map<int, std::pair<int, std::string>> sent_messages_;
+  std::string last_loading_frame_id_;
 };
 
 RenderFrameDevToolsAgentHost::FrameHostHolder::FrameHostHolder(
@@ -220,6 +228,19 @@ void RenderFrameDevToolsAgentHost::FrameHostHolder::SendMessageToClient(
     pending_messages_.push_back(std::make_pair(session_id, message));
   else
     agent_->SendMessageToClient(session_id, message);
+
+  // Store frameId when the frame starts loading to use it in case if the
+  // pending frame host is discarded.
+  if (last_loading_frame_id_.empty() &&
+      message.find("Page.frameStartedLoading") != std::string::npos) {
+    scoped_ptr<base::Value> message_content = base::JSONReader::Read(message);
+    base::DictionaryValue* message_dict;
+    if (message_content && message_content->GetAsDictionary(&message_dict)) {
+      base::DictionaryValue* params;
+      if (message_dict->GetDictionary("params", &params))
+        params->GetString("frameId", &last_loading_frame_id_);
+    }
+  }
 }
 
 void RenderFrameDevToolsAgentHost::FrameHostHolder::Suspend() {
@@ -390,7 +411,7 @@ void RenderFrameDevToolsAgentHost::SetPending(RenderFrameHostImpl* host) {
   // Can only be null in constructor.
   if (current_)
     current_->Suspend();
-  pending_->Suspend();
+  // Don't suspend pending_ as it may break clients.
 
   UpdateProtocolHandlers(host);
 }
@@ -724,8 +745,19 @@ void RenderFrameDevToolsAgentHost::DidFailProvisionalLoad(
     bool was_ignored_by_handler) {
   if (browser_side_navigation)
     return;
-  if (pending_ && pending_->host() == render_frame_host)
+  if (pending_ && pending_->host() == render_frame_host) {
+    // When a pending cross-process navigation gets cancelled, the client does
+    // not receive frameStoppedLoading event, which can cause problems with
+    // further operation. Forge the event to avoid that.
+    if (!pending_->suspended() && !pending_->last_loading_frame_id().empty()) {
+      SendMessageToClient(
+          session_id(),
+          "{\"method\":\"Page.frameStoppedLoading\",\"params\":"
+          "{\"frameId\":\"" + pending_->last_loading_frame_id() + "\"}}");
+    }
+
     DiscardPending();
+  }
 }
 
 void RenderFrameDevToolsAgentHost::