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

chrome/browser/prerender/prerender_link_manager.cc

Index: chrome/browser/prerender/prerender_link_manager.cc
diff --git a/chrome/browser/prerender/prerender_link_manager.cc b/chrome/browser/prerender/prerender_link_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..57a954c011a211c5747435f8aa6f3cdf4321bd20
--- /dev/null
+++ b/chrome/browser/prerender/prerender_link_manager.cc
@@ -0,0 +1,125 @@
+// 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();
+  }
+
+  if (!manager_->AddPrerenderFromLinkRelPrerender(
+          child_id, render_view_route_id, url, referrer,
+          size, session_storage_namespace))
+    return false;

[mmenke, 2012/04/30 18:35:22]

nit:  Add braces when the antecedent takes more than one line.

[gavinp, 2012/04/30 23:55:39]

Done.

+  const ChildAndPrerenderIdPair child_and_prerender_id(child_id, prerender_id);
+  DCHECK(!ids_to_url_map_.count(child_and_prerender_id));

[mmenke, 2012/04/30 18:35:22]

nit:  DCHECK_EQ(0, ids_to_url_map_.count(child_and_prerender_id)); is generally
preferred.

[gavinp, 2012/04/30 23:55:39]

Done.

+  ids_to_url_map_.insert(std::make_pair(child_and_prerender_id, url));
+  return true;
+}
+
+void PrerenderLinkManager::OnCancelPrerender(int prerender_id,
+                                             int child_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, 2012/04/30 18:35:22]

Weird case 1:  url is being prerendered by a prerendered page.   We won't
cancel, and will start prerendering if we swap in the prerendered page.

Weird case 2:  url is being prerendered by both a prerendered page and a
non-prerendered page.  On the final cancel, we'll cancel the prerender, but
we'll start again when swapping in the prerendered page.

Think they're beyond the scope of this CL, and probably beyond worth worrying
about at all (Other than the fact we don't crash on them), but thought I'd
mention them.

[gavinp, 2012/04/30 23:55:39]

These do make me sad all the same.

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

[dominich, 2012/04/30 15:52:05]

I believe this check is redundant. You're passing in a key_type rather than an
iterator so erase is safe (and will return the number of elements removed).

[gavinp, 2012/04/30 23:55:39]

Done.

+    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);

[dominich, 2012/04/30 15:52:05]

I wonder, given the expected size of the map, if it would be more efficient to
iterate through the whole thing and check child_id and prerender_id manually.

Actually, given the expected size of the map, it would probably be more
efficient to store the ids_to_url_map_ as a std::vector<std::pair<child_id,
prerender_id>, GURL> as they'll be contiguous in memory and hence more cacheable
for these loops.

Nits, of course.

+       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(prerender_ids_to_abandon.front(), child_id);
+    prerender_ids_to_abandon.pop();
+  }
+}
+
+bool PrerenderLinkManager::IsEmpty() const {
+  return ids_to_url_map_.empty();
+}
+
+}  // namespace prerender
+