Add resource_coordinator::LifecycleUnit::GetID().

This method returns a unique id representing the LifecycleUnit. It
is required to support the chrome://discards/ page.

Bug: 775644
Change-Id: I5975e625337708cc57beca0a5d551e6352c51b6a
Reviewed-on: https://chromium-review.googlesource.com/789250
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: Chris Hamilton <chrisha@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521363}

chrome/browser/resource_coordinator/lifecycle_unit.cc

@@ -19,4 +19,13 @@ bool LifecycleUnit::SortKey::operator>(const SortKey& other) const {
   return last_focused_time > other.last_focused_time;
 }
 
+LifecycleUnit::LifecycleUnit() = default;
+LifecycleUnit::~LifecycleUnit() = default;
+
+uint32_t LifecycleUnit::GetID() const {
+  return id_;
+}
+
+uint32_t LifecycleUnit::next_id_ = 0;
+
 }  // namespace resource_coordinator

chrome/browser/resource_coordinator/lifecycle_unit.h

@@ -5,9 +5,11 @@
 #ifndef CHROME_BROWSER_RESOURCE_COORDINATOR_LIFECYCLE_UNIT_H_
 #define CHROME_BROWSER_RESOURCE_COORDINATOR_LIFECYCLE_UNIT_H_
 
+#include <stdint.h>
 #include <string>
 
 #include "base/containers/flat_set.h"
+#include "base/macros.h"
 #include "base/strings/string16.h"
 #include "base/time/time.h"
 #include "chrome/browser/resource_coordinator/discard_reason.h"
@@ -41,7 +43,11 @@ class LifecycleUnit {
     base::TimeTicks last_focused_time;
   };
 
-  virtual ~LifecycleUnit() = default;
+  LifecycleUnit();
+  virtual ~LifecycleUnit();
+
+  // Returns a unique id representing this LifecycleUnit.
+  uint32_t GetID() const;
 
   // Returns a title describing this LifecycleUnit, or an empty string if no
   // title is available.
@@ -84,6 +90,14 @@ class LifecycleUnit {
   // in the same process(es) than if we discard individual LifecycleUnits.
   // https://crbug.com/775644
   virtual bool Discard(DiscardReason discard_reason) = 0;
+
+ private:
+  static uint32_t next_id_;
+
+  // A unique id representing this LifecycleUnit.
+  const uint32_t id_ = ++next_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(LifecycleUnit);
 };
 
 using LifecycleUnitSet = base::flat_set<LifecycleUnit*>;

chrome/browser/resource_coordinator/lifecycle_unit_unittest.cc

@@ -4,11 +4,33 @@
 
 #include "chrome/browser/resource_coordinator/lifecycle_unit.h"
 
+#include "base/macros.h"
 #include "base/time/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace resource_coordinator {
 
+namespace {
+
+class DummyLifecycleUnit : public LifecycleUnit {
+ public:
+  DummyLifecycleUnit() = default;
+
+  // LifecycleUnit:
+  base::string16 GetTitle() const override { return base::string16(); }
+  std::string GetIconURL() const override { return std::string(); }
+  SortKey GetSortKey() const override { return SortKey(); }
+  State GetState() const override { return State::LOADED; }
+  int GetEstimatedMemoryFreedOnDiscardKB() const override { return 0; }
+  bool CanDiscard(DiscardReason reason) const override { return false; }
+  bool Discard(DiscardReason discard_reason) override { return false; }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DummyLifecycleUnit);
+};
+
+}  // namespace
+
 TEST(LifecycleUnitTest, SortKeyComparison) {
   constexpr base::TimeTicks kBaseTime;
   LifecycleUnit::SortKey a(kBaseTime);
@@ -40,4 +62,20 @@ TEST(LifecycleUnitTest, SortKeyComparison) {
   EXPECT_FALSE(c > c);
 }
 
+// Verify that GetID() returns different ids for different LifecycleUnits, but
+// always the same id for the same LifecycleUnit.
+TEST(LifecycleUnitTest, GetID) {
+  DummyLifecycleUnit a;
+  DummyLifecycleUnit b;
+  DummyLifecycleUnit c;
+
+  EXPECT_NE(a.GetID(), b.GetID());
+  EXPECT_NE(a.GetID(), c.GetID());
+  EXPECT_NE(b.GetID(), c.GetID());
+
+  EXPECT_EQ(a.GetID(), a.GetID());
+  EXPECT_EQ(b.GetID(), b.GetID());
+  EXPECT_EQ(c.GetID(), c.GetID());
+}
+
 }  // namespace resource_coordinator