Diagnose renderer-side crash with browser-side stack trace.

content/browser/renderer_host/render_view_host_impl.cc

Index: content/browser/renderer_host/render_view_host_impl.cc
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index 4672bccd6fc703e014b5b2d022763a8adba569f0..1aabbab15a7aad47a0401418ca3b3ea773de8999 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -11,6 +11,7 @@
 
 #include "base/callback.h"
 #include "base/command_line.h"
+#include "base/debug/dump_without_crashing.h"
 #include "base/i18n/rtl.h"
 #include "base/json/json_reader.h"
 #include "base/message_loop/message_loop.h"
@@ -46,6 +47,7 @@
 #include "content/common/frame_messages.h"
 #include "content/common/input_messages.h"
 #include "content/common/inter_process_time_ticks_converter.h"
+#include "content/common/site_isolation_policy.h"
 #include "content/common/speech_recognition_messages.h"
 #include "content/common/swapped_out_messages.h"
 #include "content/common/view_messages.h"
@@ -300,6 +302,15 @@ bool RenderViewHostImpl::CreateRenderView(
   CHECK(main_frame_routing_id_ != MSG_ROUTING_NONE ||
         proxy_route_id != MSG_ROUTING_NONE);

[Charlie Reis, 2016/01/25 20:29:15]

Note: There's an existing set of crashes on this line (with no bug filed yet):
https://crash.corp.google.com/browse?q=product.name%3D%27Chrome%27%20AND%20%2...

The new ones I'm adding should be easy to distinguish, since their magic
signature will start with "[Dump without crash]".

 
+  // If swappedout:// is disabled, we should not set both main_frame_routing_id_
+  // and proxy_route_id.  Log cases that this happens (without crashing) to
+  // track down https://crbug.com/574245.
+  // TODO(creis): Remove this once we've found the cause.
+  if (SiteIsolationPolicy::IsSwappedOutStateForbidden() &&
+      main_frame_routing_id_ != MSG_ROUTING_NONE &&
+      proxy_route_id != MSG_ROUTING_NONE)
+    base::debug::DumpWithoutCrashing();

[nasko, 2016/01/25 21:31:48]

Multiline if statement requires {}.

[Charlie Reis, 2016/01/25 22:07:11]

As we chatted about, I think it's optional in this case (since the statement is
one line), plus we'll be reverting it soon anyway.  I'll go ahead with this
patchset to make sure it's in tomorrow's canary.

Reference:
https://google.github.io/styleguide/cppguide.html#Conditionals

+
   GetWidget()->set_renderer_initialized(true);
 
   // Ensure the RenderView starts with a next_page_id larger than any existing