Per-host V8 histograms.

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 04f2a9655b6cdfd3a3f36df4e1799bc861c54bda..a62932114b625c4c9d235f4cad7480a3e3e33620 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -3211,6 +3211,15 @@ void RenderViewImpl::didCommitProvisionalLoad(WebFrame* frame,
 
   // Check whether we have new encoding name.
   UpdateEncoding(frame, frame->view()->pageEncoding().utf8());
+
+  if (!frame->parent()) {  // Only for top frames.
+    RenderThreadImpl* render_thread_impl = RenderThreadImpl::current();
+    if (render_thread_impl) {  // Can be NULL in tests.
+      render_thread_impl->histogram_customizer()->
+          RenderViewNavigatedToHost(GURL(GetLoadingUrl(frame)).host(),
+                                    g_view_map.Get().size());
+    }
+  }
 }
 
 void RenderViewImpl::didClearWindowObject(WebFrame* frame) {