Add LifecycleUnit::Freeze().

A frozen LifecycleUnit can't use the CPU.

Note: This feature will  be test by a browser test in
https://chromium-review.googlesource.com/c/chromium/src/+/980742/5/chrome/browser/resource_coordinator/tab_manager_browsertest.cc#814

Bug: 775644
Change-Id: I5b5aac616e7a5d28b61f379d841da2b75420300d
Reviewed-on: https://chromium-review.googlesource.com/981396
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Fadi Meawad <fmeawad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547714}

chrome/browser/resource_coordinator/discard_metrics_lifecycle_unit_observer_unittest.cc

@@ -47,6 +47,7 @@ class DummyLifecycleUnit : public LifecycleUnitBase {
   base::string16 GetTitle() const override { return base::string16(); }
   std::string GetIconURL() const override { return std::string(); }
   SortKey GetSortKey() const override { return SortKey(last_focused_time_); }
+  bool Freeze() override { return false; }
   int GetEstimatedMemoryFreedOnDiscardKB() const override { return 0; }
   bool CanDiscard(DiscardReason reason) const override { return false; }
   bool Discard(DiscardReason discard_reason) override { return false; }

chrome/browser/resource_coordinator/lifecycle_unit.h

@@ -78,6 +78,10 @@ class LifecycleUnit {
   // Returns the last time that the visibility of the LifecycleUnit changed.
   virtual base::TimeTicks GetLastVisibilityChangeTime() const = 0;
 
+  // Freezes this LifecycleUnit, i.e. prevents it from using the CPU. Returns
+  // true on success.
+  virtual bool Freeze() = 0;
+
   // Returns the estimated number of kilobytes that would be freed if this
   // LifecycleUnit was discarded.
   //

chrome/browser/resource_coordinator/lifecycle_unit_base_unittest.cc

@@ -45,6 +45,7 @@ class DummyLifecycleUnit : public LifecycleUnitBase {
   std::string GetIconURL() const override { return std::string(); }
   SortKey GetSortKey() const override { return SortKey(); }
   State GetState() const override { return State::LOADED; }
+  bool Freeze() override { return false; }
   int GetEstimatedMemoryFreedOnDiscardKB() const override { return 0; }
   bool CanDiscard(DiscardReason reason) const override { return false; }
   bool Discard(DiscardReason discard_reason) override { return false; }

chrome/browser/resource_coordinator/tab_lifecycle_unit.cc

@@ -99,6 +99,16 @@ LifecycleUnit::SortKey TabLifecycleUnitSource::TabLifecycleUnit::GetSortKey()
   return SortKey(last_focused_time_);
 }
 
+bool TabLifecycleUnitSource::TabLifecycleUnit::Freeze() {
+  // Can't freeze tabs that are already discarded or frozen.
+  // TODO(fmeawad): Don't freeze already frozen tabs.
+  if (GetState() != State::LOADED)
+    return false;
+
+  GetWebContents()->FreezePage();
+  return true;
+}
+
 int TabLifecycleUnitSource::TabLifecycleUnit::
     GetEstimatedMemoryFreedOnDiscardKB() const {
   // TODO(fdoray): Implement this. https://crbug.com/775644
@@ -297,6 +307,10 @@ bool TabLifecycleUnitSource::TabLifecycleUnit::DiscardTab() {
   return Discard(DiscardReason::kExternal);
 }
 
+bool TabLifecycleUnitSource::TabLifecycleUnit::FreezeTab() {
+  return Freeze();
+}
+
 bool TabLifecycleUnitSource::TabLifecycleUnit::IsDiscarded() const {
   return GetState() == State::DISCARDED;
 }

chrome/browser/resource_coordinator/tab_lifecycle_unit.h

@@ -75,6 +75,7 @@ class TabLifecycleUnitSource::TabLifecycleUnit
   base::string16 GetTitle() const override;
   std::string GetIconURL() const override;
   SortKey GetSortKey() const override;
+  bool Freeze() override;
   int GetEstimatedMemoryFreedOnDiscardKB() const override;
   bool CanDiscard(DiscardReason reason) const override;
   bool Discard(DiscardReason discard_reason) override;
@@ -84,6 +85,7 @@ class TabLifecycleUnitSource::TabLifecycleUnit
   bool IsMediaTab() const override;
   bool IsAutoDiscardable() const override;
   void SetAutoDiscardable(bool auto_discardable) override;
+  bool FreezeTab() override;
   bool DiscardTab() override;
   bool IsDiscarded() const override;
   int GetDiscardCount() const override;

chrome/browser/resource_coordinator/tab_lifecycle_unit_external.h

@@ -35,6 +35,9 @@ class TabLifecycleUnitExternal {
   // Allows/disallows this tab to be automatically discarded.
   virtual void SetAutoDiscardable(bool auto_discardable) = 0;
 
+  // Freezes the tab.
+  virtual bool FreezeTab() = 0;
+
   // Discards the tab.
   virtual bool DiscardTab() = 0;