Ensure that the browser’s copy of page id is in sync with the renderer’s.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index b6ff8109294e6b8da9454c4cee3f9241cf83a6e8..d36ed9578b3e8484ce32f9e12b2e300e1cc75a1a 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -7,6 +7,7 @@
 #include <utility>
 
 #include "base/command_line.h"
+#include "base/debug/crash_logging.h"
 #include "base/debug/trace_event.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
@@ -3629,8 +3630,29 @@ void WebContentsImpl::RenderViewDeleted(RenderViewHost* rvh) {
 }
 
 void WebContentsImpl::UpdateState(RenderViewHost* rvh,
+                                  int32 browser_page_id,
                                   int32 page_id,
                                   const PageState& page_state) {
+  if (browser_page_id != page_id) {
+    base::debug::SetCrashKeyValue("renderer_id", base::IntToString(page_id));

[Charlie Reis, 2014/09/26 19:30:11]

nit: Let's spell these out at renderer_page_id and browser_page_id, in case
anyone else looks at them.

[Avi (use Gerrit), 2014/09/26 19:58:18]

Done.

+    base::debug::SetCrashKeyValue("browser_id",
+                                  base::IntToString(browser_page_id));
+    if (rvh != GetRenderViewHost() &&
+        !GetRenderManager()->IsRVHOnSwappedOutList(
+            static_cast<RenderViewHostImpl*>(rvh))) {
+      base::debug::SetCrashKeyValue("quick_discard", "yes");

[Charlie Reis, 2014/09/26 19:30:11]

What's quick_discard?  Can you add a comment for this theory?

[Avi (use Gerrit), 2014/09/26 19:58:18]

Done.

+    } else {
+      base::debug::SetCrashKeyValue("quick_discard", "no");
+      int entry_index = controller_.GetEntryIndexWithPageID(
+          rvh->GetSiteInstance(), page_id);
+      bool renderer_id_matches_last_commmitted_entry =
+          entry_index == controller_.GetLastCommittedEntryIndex();
+      base::debug::SetCrashKeyValue(
+          "is_last_committed_entry",
+          renderer_id_matches_last_commmitted_entry ? "yes" : "no");

[Charlie Reis, 2014/09/26 19:30:11]

Maybe it would be more useful (and easier) to report the last committed entry's
page ID, if there is a last committed entry?  That would let us compare it
against browser_page_id as well in the crash report.

And I think we can do that whether it's the "quick_discard" case or not, though
maybe I don't understand that case.

[Avi (use Gerrit), 2014/09/26 19:58:18]

Done.

+    }
+    CHECK(false);
+  }
   // Ensure that this state update comes from either the active RVH or one of
   // the swapped out RVHs.  We don't expect to hear from any other RVHs.
   // TODO(nasko): This should go through RenderFrameHost.