Introduce RenderProcessHostObserver, use it in its first client.

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 9e32d8ce267e3416a69a5be56b2ba7f58e14b187..0c577415171629da2f4fb2e38e6924dfcf8b6b4d 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -117,6 +117,7 @@
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_process_host_factory.h"
+#include "content/public/browser/render_process_host_observer.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/render_widget_host_iterator.h"
 #include "content/public/browser/resource_context.h"
@@ -359,6 +360,7 @@ RenderProcessHostImpl::RenderProcessHostImpl(
     bool is_guest)
         : fast_shutdown_started_(false),
           deleting_soon_(false),
+          deletion_callback_called_(false),
           pending_views_(0),
           visible_widgets_(0),
           backgrounded_(true),
@@ -400,6 +402,12 @@ RenderProcessHostImpl::RenderProcessHostImpl(
 }
 
 RenderProcessHostImpl::~RenderProcessHostImpl() {
+  if (!deletion_callback_called_) {
+    FOR_EACH_OBSERVER(RenderProcessHostObserver,
+                      observers_,
+                      RenderProcessHostDestroyed(this));
+  }
+
   ChildProcessSecurityPolicyImpl::GetInstance()->Remove(GetID());
 
   if (gpu_observer_registered_) {
@@ -772,6 +780,15 @@ void RenderProcessHostImpl::RemoveRoute(int32 routing_id) {
     Cleanup();
 }
 
+void RenderProcessHostImpl::AddObserver(RenderProcessHostObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void RenderProcessHostImpl::RemoveObserver(
+    RenderProcessHostObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
 bool RenderProcessHostImpl::WaitForBackingStoreMsg(
     int render_widget_id,
     const base::TimeDelta& max_delay,
@@ -1362,6 +1379,10 @@ void RenderProcessHostImpl::Cleanup() {
   // When no other owners of this object, we can delete ourselves
   if (listeners_.IsEmpty()) {
     DCHECK_EQ(0, pending_views_);
+    FOR_EACH_OBSERVER(RenderProcessHostObserver,
+                      observers_,
+                      RenderProcessHostDestroyed(this));

[jam, 2013/11/15 22:42:23]

why isn't this enough, i.e. why do we need to do this in the destructor as well?

+    deletion_callback_called_ = true;
     NotificationService::current()->Notify(
         NOTIFICATION_RENDERER_PROCESS_TERMINATED,
         Source<RenderProcessHost>(this),