[TooManyTabs] Add TabNavigationThrottle

chrome/browser/resource_coordinator/tab_manager.cc

Index: chrome/browser/resource_coordinator/tab_manager.cc
diff --git a/chrome/browser/resource_coordinator/tab_manager.cc b/chrome/browser/resource_coordinator/tab_manager.cc
index c2b5150b795c23e21d1e97cbe43d51ba2ba9316e..2e9cc7c6a79e12f209e22715a3b2b3453d01a894 100644
--- a/chrome/browser/resource_coordinator/tab_manager.cc
+++ b/chrome/browser/resource_coordinator/tab_manager.cc
@@ -12,7 +12,6 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
-#include "base/command_line.h"
 #include "base/feature_list.h"
 #include "base/macros.h"
 #include "base/memory/memory_pressure_monitor.h"
@@ -43,12 +42,12 @@
 #include "chrome/browser/ui/tabs/tab_utils.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_features.h"
-#include "chrome/common/chrome_switches.h"
 #include "chrome/common/url_constants.h"
 #include "components/metrics/system_memory_stats_recorder.h"
 #include "components/variations/variations_associated_data.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/navigation_controller.h"
+#include "content/public/browser/navigation_handle.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/page_importance_signals.h"
@@ -111,6 +110,7 @@ TabManager::TabManager()
 #endif
       browser_tab_strip_tracker_(this, nullptr, nullptr),
       test_tick_clock_(nullptr),
+      loading_contents_(nullptr),
       weak_ptr_factory_(this) {
 #if defined(OS_CHROMEOS)
   delegate_.reset(new TabManagerDelegate(weak_ptr_factory_.GetWeakPtr()));
@@ -786,6 +786,8 @@ void TabManager::ActiveTabChanged(content::WebContents* old_contents,
     GetWebContentsData(old_contents)
         ->set_time_to_purge(GetTimeToPurge(min_time_to_purge_));
   }
+
+  ResumeTabNavigationIfNeeded(new_contents);
 }
 
 void TabManager::TabInsertedAt(TabStripModel* tab_strip_model,
@@ -875,4 +877,58 @@ bool TabManager::CanOnlyDiscardOnce() const {
 #endif
 }
 
+content::NavigationThrottle::ThrottleCheckResult
+TabManager::MaybeThrottleNavigation(
+    content::NavigationHandle* navigation_handle) {
+  if (!ShouldDelayNavigation(navigation_handle)) {
+    loading_contents_ = navigation_handle->GetWebContents();
+    return content::NavigationThrottle::PROCEED;
+  }
+
+  pending_navigations_.push_back(navigation_handle);
+  return content::NavigationThrottle::DEFER;
+}
+
+bool TabManager::ShouldDelayNavigation(
+    content::NavigationHandle* navigation_handle) const {
+  if (!navigation_handle)
+    return false;
+
+  // Do not throttle the navigation if no tab is currently loading.
+  if (!loading_contents_) {
+    return false;
+  }
+
+  return true;
+}
+
+void TabManager::HasFinishedLoadingTab(content::WebContents* contents) {
+  loading_contents_ = nullptr;
+
+  while (!pending_navigations_.empty()) {
+    content::NavigationHandle* navigation_handle = pending_navigations_.front();
+    pending_navigations_.erase(pending_navigations_.begin());
+
+    if (navigation_handle) {
+      loading_contents_ = navigation_handle->GetWebContents();
+      navigation_handle->Resume();
+      break;
+    }
+  }
+}
+
+void TabManager::ResumeTabNavigationIfNeeded(content::WebContents* contents) {
+  auto it = pending_navigations_.begin();
+  while (it != pending_navigations_.end()) {
+    content::NavigationHandle* navigation_handle = *it;
+    if (navigation_handle && navigation_handle->GetWebContents() == contents) {
+      loading_contents_ = navigation_handle->GetWebContents();
+      navigation_handle->Resume();
+      pending_navigations_.erase(it);
+      break;
+    }
+    it++;
+  }
+}
+
 }  // namespace resource_coordinator