Enable resource prefetch from the browser process.

chrome/renderer/prefetch_helper.cc

Index: chrome/renderer/prefetch_helper.cc
diff --git a/chrome/renderer/prefetch_helper.cc b/chrome/renderer/prefetch_helper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..efcf31da4b93dc20fdc79476893a108a0cb9148a
--- /dev/null
+++ b/chrome/renderer/prefetch_helper.cc
@@ -0,0 +1,73 @@
+// 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/renderer/prefetch_helper.h"
+
+#include "chrome/common/prefetch_messages.h"
+#include "content/public/renderer/render_frame.h"
+#include "third_party/WebKit/public/platform/WebURLLoader.h"
+#include "third_party/WebKit/public/platform/WebURLLoaderClient.h"
+#include "third_party/WebKit/public/web/WebFrame.h"
+#include "third_party/WebKit/public/web/WebURLLoaderOptions.h"
+
+namespace prefetch {
+
+class PrefetchHelper::PrefetchManager : public blink::WebURLLoaderClient {
+ public:
+  PrefetchManager() { }

[jochen (gone - plz use gerrit), 2014/06/13 16:42:55]

nit. no space between { } (did you clang-format?)

[tburkard, 2014/06/13 18:35:46]

obsolete comment

+
+  virtual ~PrefetchManager() {
+    STLDeleteElements(&loader_set_);

[jochen (gone - plz use gerrit), 2014/06/13 16:42:56]

what happens if the manager is deleted while loads are still ongoing? Can we
have a test for this?

[tburkard, 2014/06/13 18:35:46]

will add a test for this later (will send out a new update, before committing),
just wanted to get out this revised version first.

+  }
+
+  void AddPrefetch(blink::WebFrame* frame, const GURL& url) {
+    blink::WebURLRequest request(url);
+    request.setTargetType(blink::WebURLRequest::TargetIsPrefetch);
+    blink::WebURLLoaderOptions options;
+    options.allowCredentials = true;
+    options.crossOriginRequestPolicy =
+        blink::WebURLLoaderOptions::CrossOriginRequestPolicyAllow;
+    blink::WebURLLoader* loader = frame->createAssociatedURLLoader(options);
+    loader->loadAsynchronously(request, this);
+    loader_set_.insert(loader);
+  }
+
+  // blink::WebURLLoaderClient implementation.
+  virtual void didFinishLoading(blink::WebURLLoader* loader,
+                                double finishTime,
+                                int64_t totalEncodedDataLength) OVERRIDE {
+    loader_set_.erase(loader);
+  }
+  virtual void didFail(blink::WebURLLoader* loader,
+                       const blink::WebURLError& error) OVERRIDE {
+    loader_set_.erase(loader);
+  }
+
+ private:
+  std::set<blink::WebURLLoader*> loader_set_;
+};

[jochen (gone - plz use gerrit), 2014/06/13 16:42:56]

nit. disallow copy & assign

[tburkard, 2014/06/13 18:35:46]

obsolete comment

+
+PrefetchHelper::PrefetchHelper(content::RenderFrame* render_frame)
+    : content::RenderFrameObserver(render_frame),
+      prefetch_manager_(new PrefetchManager()) {
+}
+
+PrefetchHelper::~PrefetchHelper() {
+}
+
+bool PrefetchHelper::OnMessageReceived(
+    const IPC::Message& message) {
+  IPC_BEGIN_MESSAGE_MAP(PrefetchHelper, message)
+    IPC_MESSAGE_HANDLER(PrefetchMsg_Prefetch, OnPrefetch)
+  IPC_END_MESSAGE_MAP()
+  // Return false on ViewMsg_SetIsPrefetching so other observers can see the
+  // message.

[jam, 2014/06/13 16:44:37]

i dont think you need this behavior for this ipc, at least not yet. so do this
block with a standard handled return value that is set inside the macros

[tburkard, 2014/06/13 18:35:45]

Done. Does this look ok?

+  return false;
+}
+
+void PrefetchHelper::OnPrefetch(const GURL& url) {
+  prefetch_manager_->AddPrefetch(render_frame()->GetWebFrame(), url);

[jochen (gone - plz use gerrit), 2014/06/13 16:42:56]

what's the reason you use a separate class here?

[jkarlin, 2014/06/13 16:53:46]

Also, I'm adding a chrome/browser/prefetch/prefetch_manager.h+cc so would prefer
not to have another class with the same name.

[tburkard, 2014/06/13 18:35:46]

Done.

[tburkard, 2014/06/13 18:35:46]

Done.

+}
+
+}  // namespace prefetch