Check for already existing entry when adding to SiteProcessMap.

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 2c48d780f0fd99df89d492dc61abe6e947cd9d78..b43a82bc7d69c636a63781f213e1c3809dbae558 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -333,7 +333,12 @@ class SiteProcessMap : public base::SupportsUserData::Data {
   SiteProcessMap() {}
 
   void RegisterProcess(const std::string& site, RenderProcessHost* process) {
-    map_[site] = process;
+    SiteToProcessMap::iterator i = map_.find(site);
+    if (i != map_.end()) {
+      CHECK_EQ(i->second, process);

[Devlin, 2017/03/11 01:52:18]

Looks like this CHECK is failing on bots :(

[nasko, 2017/03/13 17:22:03]

Yes, I'm purposefully hitting it with my test too :). It was there to see how
broken things are. I will submit this CL without it and follow up with a
DumpWithoutCrashing, so we can understand whether this happens in practice. 

+    } else {
+      map_[site] = process;
+    }
   }
 
   RenderProcessHost* FindProcess(const std::string& site) {