[TooManyTabs] Add TabNavigationThrottle

chrome/browser/resource_coordinator/background_tab_navigation_throttle.cc

Index: chrome/browser/resource_coordinator/background_tab_navigation_throttle.cc
diff --git a/chrome/browser/resource_coordinator/background_tab_navigation_throttle.cc b/chrome/browser/resource_coordinator/background_tab_navigation_throttle.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6a1c3c9871b4119cb01a88255cfa9f5650bad046
--- /dev/null
+++ b/chrome/browser/resource_coordinator/background_tab_navigation_throttle.cc
@@ -0,0 +1,77 @@
+// Copyright 2017 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/resource_coordinator/background_tab_navigation_throttle.h"
+
+#include "base/feature_list.h"
+#include "base/memory/ptr_util.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/resource_coordinator/tab_manager.h"
+#include "chrome/browser/search/search.h"
+#include "chrome/common/chrome_features.h"
+#include "content/public/browser/navigation_handle.h"
+#include "content/public/browser/web_contents.h"
+
+namespace resource_coordinator {
+
+// static
+std::unique_ptr<BackgroundTabNavigationThrottle>
+BackgroundTabNavigationThrottle::MaybeCreateThrottleFor(
+    content::NavigationHandle* navigation_handle) {
+  if (!base::FeatureList::IsEnabled(features::kStaggeredBackgroundTabOpen))
+    return nullptr;
+
+  // Never delay foreground tabs.
+  if (navigation_handle->GetWebContents()->IsVisible())
+    return nullptr;
+
+  // Never delay the tab when there is opener, so the created window can talk
+  // to the creator immediately.
+  if (navigation_handle->GetWebContents()->HasOpener())
+    return nullptr;
+
+  // Only delay the first navigation in a newly created tab.
+  if (!navigation_handle->GetWebContents()
+           ->GetController()
+           .IsInitialNavigation()) {
+    return nullptr;
+  }
+
+  // Only consider throttling common URLs, i.e., HTTP/HTTPS and common
+  // chrome:// UI URLs, for main frames.

[chrisha, 2017/06/15 21:02:24]

I would suggest something even stronger:

chrome:// tabs should actually just be permanently delayed until made visible,
as they don't require any remote data at all.

[Zhen Wang, 2017/06/19 23:00:12]

That sounds good to me. For this CL, it tries to focus on the navigation part.
The algorithm used is very simple. I will have follow-up CLs to use better
algorithms.

This will probably be updated to use a different filtering method. I am waiting
for Charlie's reply on this.

+  if (!navigation_handle->IsInMainFrame() ||
+      (!navigation_handle->GetURL().SchemeIsHTTPOrHTTPS() &&
+       !TabManager::IsInternalPage(navigation_handle->GetURL()))) {
+    return nullptr;
+  }
+
+  // Do not delay the NTP, which in some cases has an HTTPS URL.

[chrisha, 2017/06/15 21:02:24]

Why? If an NTP is opened as a background tab it should be delayed indefinitely,
much like any other chrome:// tab (we should arrange to set the title somehow,
however).

[Zhen Wang, 2017/06/19 23:00:12]

I was copying this part from another navigation throttle. But I think your point
makes sense.

For the title, I am not quite sure how to do it. Because before loading, we do
not even know the title and favicon.

[chrisha, 2017/06/20 18:26:54]

Take a peek at what session restore does, it might work here as well:

https://cs.chromium.org/chromium/src/components/favicon/core/favicon_driver_i...

I'd say we should always be setting the favicon when possible, even if the load
is deferred.

I'm not sure if there's a similar way for us to set the expected title... maybe
from the history database? I'd at least leave a TODO to explore this.

[Zhen Wang, 2017/07/06 18:26:12]

I added a TODO for this in tab_manager.cc.

+  if (search::IsNTPURL(
+          navigation_handle->GetURL(),
+          Profile::FromBrowserContext(
+              navigation_handle->GetWebContents()->GetBrowserContext()))) {
+    return nullptr;
+  }
+

[chrisha, 2017/06/15 21:02:24]

Where are we detecting if the new tab is in the background or not? Couldn't we
skip creating the throttle entirely in this case?

[Zhen Wang, 2017/06/19 23:00:12]

This is done above after the feature flag check (line 27).

[chrisha, 2017/06/20 18:26:54]

Clearly I'm blind :)

+  return base::MakeUnique<BackgroundTabNavigationThrottle>(navigation_handle);
+}
+
+const char* BackgroundTabNavigationThrottle::GetNameForLogging() {
+  return "BackgroundTabNavigationThrottle";
+}
+
+BackgroundTabNavigationThrottle::BackgroundTabNavigationThrottle(
+    content::NavigationHandle* navigation_handle)
+    : content::NavigationThrottle(navigation_handle) {}
+
+BackgroundTabNavigationThrottle::~BackgroundTabNavigationThrottle() {}
+
+content::NavigationThrottle::ThrottleCheckResult
+BackgroundTabNavigationThrottle::WillStartRequest() {
+  return g_browser_process->GetTabManager()->MaybeThrottleNavigation(
+      navigation_handle());
+}
+
+}  // namespace resource_coordinator