[TooManyTabs] Add TabNavigationThrottle

chrome/browser/resource_coordinator/tab_manager.h

Index: chrome/browser/resource_coordinator/tab_manager.h
diff --git a/chrome/browser/resource_coordinator/tab_manager.h b/chrome/browser/resource_coordinator/tab_manager.h
index 72fa655d0c0941118cd4ad190cc89a645c469eb9..572453d0054a6e7ec4738b1767817a24612d7e80 100644
--- a/chrome/browser/resource_coordinator/tab_manager.h
+++ b/chrome/browser/resource_coordinator/tab_manager.h
@@ -26,6 +26,7 @@
 #include "chrome/browser/resource_coordinator/tab_stats.h"
 #include "chrome/browser/ui/browser_tab_strip_tracker.h"
 #include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
+#include "content/public/browser/navigation_throttle.h"
 
 class BrowserList;
 class GURL;
@@ -36,6 +37,7 @@ class TickClock;
 }
 
 namespace content {
+class NavigationHandle;
 class WebContents;
 }
 
@@ -146,6 +148,14 @@ class TabManager : public TabStripModelObserver {
   // TODO(tasak): rename this to CanPurgeBackgroundedRenderer.
   bool CanSuspendBackgroundedRenderer(int render_process_id) const;
 
+  // Maybe throttle a tab's navigation based on current system status.
+  content::NavigationThrottle::ThrottleCheckResult MaybeThrottleNavigation(
+      content::NavigationHandle* navigation_handle);
+
+  // Notifies TabManager that one tab has finished loading. TabManager can
+  // decide which tab to load next.
+  void HasFinishedLoadingTab(content::WebContents* contents);
+
   // Returns true if |first| is considered less desirable to be killed than
   // |second|.
   static bool CompareTabStats(const TabStats& first, const TabStats& second);
@@ -154,6 +164,10 @@ class TabManager : public TabStripModelObserver {
   // the WebContents could be deleted if the user closed the tab.
   static int64_t IdFromWebContents(content::WebContents* web_contents);
 
+  // Returns true if the |url| represents an internal Chrome web UI page that
+  // can be easily reloaded and hence makes a good choice to discard.

[Charlie Reis, 2017/06/10 00:53:36]

We may not need to expose this; see my question about the call site.

[Charlie Reis, 2017/07/06 23:50:30]

I'm still hoping we don't need this.  (See
https://codereview.chromium.org/2931023002/diff/1/chrome/browser/resource_coo...)

[Zhen Wang, 2017/07/07 18:06:39]

Now moved back to private as we do not need this URL check in throttle now.

+  static bool IsInternalPage(const GURL& url);
+
  private:
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, PurgeBackgroundRenderer);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, ActivateTabResetPurgeState);
@@ -205,10 +219,6 @@ class TabManager : public TabStripModelObserver {
 
   static void PurgeMemoryAndDiscardTab();
 
-  // Returns true if the |url| represents an internal Chrome web UI page that
-  // can be easily reloaded and hence makes a good choice to discard.
-  static bool IsInternalPage(const GURL& url);
-
   // Records UMA histogram statistics for a tab discard. Record statistics for
   // user triggered discards via chrome://discards/ because that allows to
   // manually test the system.
@@ -302,6 +312,13 @@ class TabManager : public TabStripModelObserver {
   // Returns true if tabs can be discarded only once.
   bool CanOnlyDiscardOnce() const;
 
+  // Returns true if the navigation should be throttled.
+  bool ShouldThrottleNavigation(

[nasko, 2017/06/12 23:22:02]

nit: s/Throttle/Delay/ as in this case we only care about delaying the
navigation for later.

[Zhen Wang, 2017/06/13 23:33:20]

Done.

+      content::NavigationHandle* navigation_handle) const;
+
+  // Resume the tab's navigation if it is pending right now.
+  void ResumeTabNavigationIfNeeded(content::WebContents* contents);
+
   // Timer to periodically update the stats of the renderers.
   base::RepeatingTimer update_timer_;
 
@@ -365,6 +382,13 @@ class TabManager : public TabStripModelObserver {
   // List of observers that will receive notifications on state changes.
   base::ObserverList<TabManagerObserver> observers_;
 
+  // The list of navigation handles that are throttled.
+  std::vector<content::NavigationHandle*> pending_navigations_;
+
+  // The tab that is currently loading. If multiple tabs are loading
+  // simultaneously, it corresponds to the lastest one.
+  content::WebContents* loading_contents_;
+
   // Weak pointer factory used for posting delayed tasks.
   base::WeakPtrFactory<TabManager> weak_ptr_factory_;