Add ExternalPrerenderRequestHandler and related API

chrome/browser/android/external_prerender_request_handler.cc

+// Copyright (c) 2013 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/android/external_prerender_request_handler.h"
+
+#include "base/android/jni_android.h"
+#include "base/android/jni_string.h"
+#include "base/strings/string16.h"
+#include "base/strings/utf_string_conversions.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/prerender/prerender_handle.h"
+#include "chrome/browser/prerender/prerender_manager.h"
+#include "chrome/browser/prerender/prerender_manager_factory.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/profiles/profile_android.h"
+#include "content/public/browser/web_contents.h"
+
+#include "jni/ExternalPrerenderRequestHandler_jni.h"
+
+using base::android::ConvertJavaStringToUTF16;
+
+namespace prerender {
+
+int ExternalPrerenderRequestHandler::AddPrerender(JNIEnv* env,
+                                                  jobject obj,
+                                                  jobject jprofile,
+                                                  jstring jurl,
+                                                  jstring jreferrer,
+                                                  jint width,
+                                                  jint height) {
+  Profile* profile = ProfileAndroid::FromProfileAndroid(jprofile);
+
+  GURL url = GURL(ConvertJavaStringToUTF16(env, jurl));
+  if (!url.is_valid())
+    return 0;
+
+  GURL referrer_url = GURL(ConvertJavaStringToUTF16(env, jreferrer));
+  content::Referrer referrer = referrer_url.is_valid() ?
+      content::Referrer(referrer_url, WebKit::WebReferrerPolicyDefault) :
+      content::Referrer();
+
+  PrerenderManager* prerender_manager =
+      prerender::PrerenderManagerFactory::GetForProfile(profile);

[cbentzel, 2013/10/30 14:40:33]

Note: It's possible for PrerenderManager to be NULL in certain cases (low-memory
devices, incognito profiles). Probably safest to check for NULL here and early
return, although it's possible to handle all of the constraints at the Java
layer.

[Yusuf, 2013/10/31 00:44:18]

Done.

+  content::WebContents* web_contents =
+      content::WebContents::Create(content::WebContents::CreateParams(profile));

[cbentzel, 2013/10/30 14:40:33]

So is this going to always create a new tab/webcontents? It feels like that
might be better to do outside this method and pass it in. What happens, for
example, if the prerender gets canceled?

[Yusuf, 2013/10/31 00:44:18]

Done.

+  if (prerender_handle_.get()) {
+    prerender_handle_->OnNavigateAway();
+    // The PrerenderHandle is now owned by the PrerenderManager.
+    ignore_result(prerender_handle_.release());

[cbentzel, 2013/10/30 14:40:33]

TODO(cbentzel): Understand this.

[cbentzel, 2013/10/30 14:40:33]

TODO(cbentzel): Understand this.

+  }
+  prerender_handle_.reset(
+      prerender_manager->AddPrerenderFromExternalRequest(
+          url,
+          referrer,
+          web_contents->GetController().GetDefaultSessionStorageNamespace(),
+          gfx::Size(width, height)));
+  if (!prerender_handle_)
+    return 0;
+  return reinterpret_cast<jint>(web_contents);

[cbentzel, 2013/10/30 14:40:33]

If you are going this route definitely want reinterpret_cast<int> rather than
<jint>

However - is there a pointer type which could be used instead? Not sure if
Android has plans to go to 64-bit binaries but given that iOS has I worry that
there are cases where this will bite in the future.

[Yusuf, 2013/10/31 00:44:18]

Done.

+}
+
+void ExternalPrerenderRequestHandler::CancelCurrentPrerender(JNIEnv* env,
+                                                             jobject object) {
+  if(prerender_handle_)
+    prerender_handle_->OnCancel();
+}
+
+// static
+bool ExternalPrerenderRequestHandler::HasPrerenderedUrl(
+    Profile* profile,
+    GURL url,
+    content::WebContents* web_contents) {
+  prerender::PrerenderManager* prerender_manager =
+          prerender::PrerenderManagerFactory::GetForProfile(profile);

[cbentzel, 2013/10/30 14:40:33]

Again - probably good to check for NULL prerender_manager.

+  content::SessionStorageNamespace* session_storage_namespace = web_contents->
+      GetController().GetDefaultSessionStorageNamespace();
+
+  std::vector<content::WebContents*> contents =

[cbentzel, 2013/10/30 14:40:33]

I'm surprised that we don't have a method like this already on PrerenderManager
- but I'm assuming you checked.

[Yusuf, 2013/10/30 17:28:55]

I did check and I agree that it would be nice to have in prerender_manager. Can
I just put this in there as opposed to having it in this class?


On 2013/10/30 14:40:33, cbentzel wrote:

[cbentzel, 2013/10/30 18:45:59]

Yes.

+      prerender_manager->GetAllPrerenderingContents();
+  for (size_t i = 0; i < contents.size(); ++i) {
+    prerender::PrerenderContents* prerender_contents = prerender_manager->
+        GetPrerenderContents(contents.at(i));
+    if (prerender_contents->Matches(url, session_storage_namespace))
+      return true;
+  }
+  return false;
+}
+
+static jboolean HasPrerenderedUrl(JNIEnv* env,

[cbentzel, 2013/10/30 14:40:33]

Is this being used at all? I didn't see it declared in the header and it isn't
being used in this file as far as I can tell.

[Yusuf, 2013/10/30 17:28:55]

Calls with JNIEnv as first argument, jclass as second and no class association
are usually static calls that will come in from Java in Android. 

See ExternalPrerenderRequestHandler.java. At the end of the file there are
nativeHasPrerenderedUrl and nativeInit. We have scripts that create JNI bindings
automatically out of these.



On 2013/10/30 14:40:33, cbentzel wrote:

[cbentzel, 2013/10/30 18:45:59]

Thanks for clarifying that.

+                                  jclass clazz,
+                                  jobject jprofile,
+                                  jstring jurl,
+                                  jint web_contents_ptr) {
+    Profile* profile = ProfileAndroid::FromProfileAndroid(jprofile);
+    GURL url;
+    if (jurl != NULL)
+      url = GURL(ConvertJavaStringToUTF16(env, jurl));
+    if (!url.is_valid())
+      return false;
+
+    content::WebContents* web_contents =
+        reinterpret_cast<content::WebContents*>(web_contents_ptr);
+    return ExternalPrerenderRequestHandler::HasPrerenderedUrl(
+        profile, url, web_contents);
+}
+
+ExternalPrerenderRequestHandler::ExternalPrerenderRequestHandler() {
+}
+
+static jint Init(JNIEnv* env,

[cbentzel, 2013/10/30 14:40:33]

Is Init being used at all?

[Yusuf, 2013/10/30 17:28:55]

See above.

On 2013/10/30 14:40:33, cbentzel wrote:

+                 jclass clazz) {
+  ExternalPrerenderRequestHandler* external_handler =
+      new ExternalPrerenderRequestHandler();
+  return reinterpret_cast<jint>(external_handler);
+}
+
+bool ExternalPrerenderRequestHandler::RegisterExternalPrerenderRequestHandler(
+    JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+} // namespace prerender