Add GlobalRoutingID::operator<<.

This allows the use of, e.g.: CHECK_EQ(), making error messages clearer.

Change-Id: I0d087117e3da0cafc792ea7baa78c89febcec4ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2463281Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Tal Pressman <talp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816354}

content/public/browser/global_routing_id.h

@@ -8,6 +8,8 @@
 #include <tuple>
 
 #include "base/hash/hash.h"
+#include "base/i18n/number_formatting.h"
+#include "base/strings/stringprintf.h"
 #include "ipc/ipc_message.h"
 
 namespace content {
@@ -38,6 +40,11 @@ struct GlobalRoutingID {
   }
 };
 
+inline std::ostream& operator<<(std::ostream& os, const GlobalRoutingID& id) {
+  os << "GlobalRoutingID(" << id.child_id << ", " << id.route_id << ")";
+  return os;
+}
+
 // Same as GlobalRoutingID except the route_id must be a RenderFrameHost routing
 // id.
 struct GlobalFrameRoutingId {

content/test/web_contents_observer_consistency_checker.cc

@@ -391,7 +391,7 @@ void WebContentsObserverConsistencyChecker::EnsureStableParentValue(
     parent_ids_.insert(std::make_pair(routing_pair, parent_routing_pair));
   } else {
     GlobalRoutingID former_parent_routing_pair = it->second;
-    CHECK(former_parent_routing_pair == parent_routing_pair)
+    CHECK_EQ(former_parent_routing_pair, parent_routing_pair)
         << "RFH's parent value changed over time! That is really not good!";
   }
 }