New link rel=prerender api, using WebKit::WebPrerenderingPlatform

chrome/browser/prerender/prerender_link_manager.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/prerender/prerender_link_manager.h"
+
+#include <limits>
+#include <queue>
+#include <utility>
+
+#include "chrome/browser/prerender/prerender_contents.h"
+#include "chrome/browser/prerender/prerender_manager.h"
+#include "chrome/browser/prerender/prerender_manager_factory.h"
+#include "chrome/browser/profiles/profile.h"
+#include "content/public/browser/render_view_host.h"
+#include "content/public/browser/session_storage_namespace.h"
+#include "content/public/common/referrer.h"
+#include "googleurl/src/gurl.h"
+#include "googleurl/src/url_canon.h"
+#include "ui/gfx/size.h"
+
+using content::RenderViewHost;
+using content::SessionStorageNamespace;
+
+namespace prerender {
+
+PrerenderLinkManager::PrerenderLinkManager(PrerenderManager* manager)
+    : manager_(manager) {
+}
+
+PrerenderLinkManager::~PrerenderLinkManager() {
+}
+
+bool PrerenderLinkManager::OnAddPrerender(int child_id,
+                                          int prerender_id,
+                                          const GURL& orig_url,
+                                          const content::Referrer& referrer,
+                                          const gfx::Size& size,
+                                          int render_view_route_id) {
+  DVLOG(2) << "OnAddPrerender, child_id = " << child_id
+           << ", prerender_id = " << prerender_id
+           << ", url = " << orig_url.spec();
+  DVLOG(3) << "... render_view_route_id = " << render_view_route_id
+           << ", referrer url = " << referrer.url.spec();
+  // TODO(gavinp): Add tests to ensure fragments work, then remove this fragment
+  // clearing code.
+  url_canon::Replacements<char> replacements;
+  replacements.ClearRef();
+  const GURL url = orig_url.ReplaceComponents(replacements);
+
+  // Unit tests pass in a child_id == -1.
+  RenderViewHost* source_render_view_host = NULL;
+  SessionStorageNamespace* session_storage_namespace = NULL;
+  if (child_id != -1) {
+    source_render_view_host =
+        RenderViewHost::FromID(child_id, render_view_route_id);
+    if (!source_render_view_host || !source_render_view_host->GetView())
+      return false;
+    session_storage_namespace =
+        source_render_view_host->GetSessionStorageNamespace();
+  }

[mmenke, 2012/05/01 16:23:21]

Wonder if this block of code might not be happier living in
AddPrerenderFromLinkRelPrerender.  The fact it's not there has already been the
cause of one bug already.

Also, having this code here affects histograms, since we're no longer recording
"FINAL_STATUS_SOURCE_RENDER_VIEW_CLOSED"

[gavinp, 2012/05/01 18:50:22]

Done.
Done.

+
+  if (!manager_->AddPrerenderFromLinkRelPrerender(
+          child_id, render_view_route_id, url, referrer,
+          size, session_storage_namespace)) {
+    return false;
+  }
+  const ChildAndPrerenderIdPair child_and_prerender_id(child_id, prerender_id);
+  DCHECK_EQ(0U, ids_to_url_map_.count(child_and_prerender_id));
+  ids_to_url_map_.insert(std::make_pair(child_and_prerender_id, url));
+  return true;
+}
+
+void PrerenderLinkManager::OnCancelPrerender(int child_id, int prerender_id) {
+  DVLOG(2) << "OnCancelPrerender, child_id = " << child_id
+           << ", prerender_id = " << prerender_id;
+  const ChildAndPrerenderIdPair child_and_prerender_id(child_id, prerender_id);
+  IdPairToUrlMap::iterator id_url_iter =
+      ids_to_url_map_.find(child_and_prerender_id);
+  if (id_url_iter == ids_to_url_map_.end()) {
+    DVLOG(5) << "... canceling a prerender that doesn't exist.";
+    return;
+  }
+  const GURL url = id_url_iter->second;
+  ids_to_url_map_.erase(id_url_iter);
+  manager_->MaybeCancelPrerender(url);

[mmenke, 2012/05/01 16:23:21]

Another funky case (Again, just something to think about.  This will probably be
fixed by some of the planned changes already discussed, anyways):

A site prerenders some url.  The prerender times out.  The site prerenders the
url again (Or some other site does).  We start prerendering again.  The original
prerender request is cancelled.  We the cancel the prerender, even though the
page is still being prerendered.

[gavinp, 2012/05/01 18:50:22]

Yes.  That case should be caught by even the simplest observer interface.

+}
+
+void PrerenderLinkManager::OnAbandonPrerender(int child_id, int prerender_id) {
+  DVLOG(2) << "OnAbandonPrerender, child_id = " << child_id
+           << ", prerender_id = " << prerender_id;
+  // TODO(gavinp,cbentzel): Implement reasonable behaviour for
+  // navigation away from launcher.

[mmenke, 2012/05/01 16:23:21]

You had a comment here before on why there's no check here for whether or not
the prerender exists, like we do in OnCancelPrerender, and a TODO to add it
later.  I suggest you add back the comment, at least, and the TODO, if still
applicable.

[gavinp, 2012/05/01 18:50:22]

That comment got mooted by dominich's earlier suggestion that we not create
entries in the map where AddPrerenderFromLinkRelPrerender fails.  Previously,
the issue was that our (observer-free) WebKit implementation abandons all
prerenders on navigation away.  Now, though, some Prerenders don't even add, and
WebKit has no idea.

I'll add a single comment on this issue in front of OnCancelPrerender, since
it's the first method affected by this.

[mmenke, 2012/05/02 15:02:52]

Oh, right.  I saw the DVLOG for that case in OnCancelPrerender, and assumed it
was a DCHECK.

+  const ChildAndPrerenderIdPair child_and_prerender_id(child_id, prerender_id);
+  ids_to_url_map_.erase(child_and_prerender_id);
+}
+
+void PrerenderLinkManager::OnChannelClosing(int child_id) {
+  DVLOG(2) << "OnChannelClosing, child id = " << child_id;
+  const ChildAndPrerenderIdPair child_and_minimum_prerender_id(
+      child_id, std::numeric_limits<int>::min());
+  const ChildAndPrerenderIdPair child_and_maximum_prerender_id(
+      child_id, std::numeric_limits<int>::max());
+  std::queue<int> prerender_ids_to_abandon;
+  for (IdPairToUrlMap::iterator
+           i = ids_to_url_map_.lower_bound(child_and_minimum_prerender_id),
+           e = ids_to_url_map_.upper_bound(child_and_maximum_prerender_id);
+       i != e; ++i) {
+    prerender_ids_to_abandon.push(i->first.second);
+  }
+  while (!prerender_ids_to_abandon.empty()) {
+    DVLOG(4) << "---> abandon prerender_id = "
+             << prerender_ids_to_abandon.front();
+    OnAbandonPrerender(child_id, prerender_ids_to_abandon.front());
+    prerender_ids_to_abandon.pop();
+  }
+}
+
+bool PrerenderLinkManager::IsEmpty() const {
+  return ids_to_url_map_.empty();
+}
+
+}  // namespace prerender
+