Consolidate isolated origin subframes into existing processes.

content/browser/frame_host/render_frame_host_manager.cc

Index: content/browser/frame_host/render_frame_host_manager.cc
diff --git a/content/browser/frame_host/render_frame_host_manager.cc b/content/browser/frame_host/render_frame_host_manager.cc
index 3458260ab9293609526d43fe63ff9f9405f75952..42c7e04c9958270c688f4ee3c21fa1f3d30b1e99 100644
--- a/content/browser/frame_host/render_frame_host_manager.cc
+++ b/content/browser/frame_host/render_frame_host_manager.cc
@@ -1262,6 +1262,19 @@ RenderFrameHostManager::GetSiteInstanceForNavigation(
   // BrowserContext.
   DCHECK_EQ(new_instance->GetBrowserContext(), browser_context);
 
+  // If |new_instance| is a new SiteInstance for a subframe with an isolated
+  // origin, set its process reuse policy so that such subframes are
+  // consolidated into existing processes for that isolated origin.
+  SiteInstanceImpl* new_instance_impl =
+      static_cast<SiteInstanceImpl*>(new_instance.get());
+  auto* policy = ChildProcessSecurityPolicyImpl::GetInstance();
+  if (!frame_tree_node_->IsMainFrame() && !new_instance_impl->HasProcess() &&
+      new_instance_impl->HasSite() &&
+      policy->IsIsolatedOrigin(url::Origin(new_instance_impl->GetSiteURL()))) {

[alexmos, 2017/06/01 20:47:58]

We could consider doing this for all subframes that require a dedicated process,
not just isolated origins.  Do you think that's worth doing here or in a
followup?

[Charlie Reis, 2017/06/01 22:27:47]

I like that idea.  It would probably be safe to do here, but doing it in a
followup is probably worthwhile-- that makes it less likely that the isolated
origin case is reverted if the general case turns out to have issues.

+    new_instance_impl->set_process_reuse_policy(
+        SiteInstanceImpl::ProcessReusePolicy::REUSE_PENDING_OR_COMMITTED_SITE);
+  }
+
   return new_instance;
 }