Provide renderers with memory pressure signals.

chrome/browser/memory/tab_manager_unittest.cc

Index: chrome/browser/memory/tab_manager_unittest.cc
diff --git a/chrome/browser/memory/tab_manager_unittest.cc b/chrome/browser/memory/tab_manager_unittest.cc
index 719afca4859fa9b267e4e3ef41a344c88252c032..08f2e8f83cff6882b80aa2cff7b97d2bf30f5b1b 100644
--- a/chrome/browser/memory/tab_manager_unittest.cc
+++ b/chrome/browser/memory/tab_manager_unittest.cc
@@ -10,6 +10,7 @@
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/strings/string16.h"
+#include "base/test/simple_test_tick_clock.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "chrome/browser/memory/tab_manager_web_contents_data.h"
@@ -22,6 +23,7 @@
 #include "chrome/test/base/testing_profile.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/test/web_contents_tester.h"
+#include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
 
@@ -76,6 +78,96 @@ class MockTabStripModelObserver : public TabStripModelObserver {
   DISALLOW_COPY_AND_ASSIGN(MockTabStripModelObserver);
 };
 
+// A mock task runner. This isn't directly a TaskRunner as the reference
+// counting confuses gmock.
+class LenientMockTaskRunner {
+ public:
+  LenientMockTaskRunner() {}
+  MOCK_METHOD3(PostDelayedTask,
+               bool(const tracked_objects::Location&,
+                    const base::Closure&,
+                    base::TimeDelta));
+ private:
+  DISALLOW_COPY_AND_ASSIGN(LenientMockTaskRunner);
+};
+using MockTaskRunner = testing::StrictMock<LenientMockTaskRunner>;
+
+// Represents a pending task.
+using Task = std::pair<base::TimeTicks, base::Closure>;
+
+// Comparator used for sorting Task objects. Can't use std::pair's default
+// comparison operators because Closure's are comparable.
+struct TaskComparator {
+  bool operator()(const Task& t1, const Task& t2) const {
+    // Reverse the sort order so this can be used with a min-heap.
+    return t1.first > t2.first;
+  }
+};
+
+// A TaskRunner implementation that delegates to a MockTaskRunner for asserting
+// on task insertion order, and which stores tasks for actual later execution.
+class TaskRunnerProxy : public base::TaskRunner {
+ public:
+  TaskRunnerProxy(MockTaskRunner* mock,
+                  base::SimpleTestTickClock* clock)
+      : mock_(mock), clock_(clock) {}
+  bool RunsTasksOnCurrentThread() const override { return true; }
+  bool PostDelayedTask(const tracked_objects::Location& location,
+                       const base::Closure& closure,
+                       base::TimeDelta delta) override {
+    mock_->PostDelayedTask(location, closure, delta);
+    base::TimeTicks when = clock_->NowTicks() + delta;
+    tasks_.push_back(Task(when, closure));
+    // Use 'greater' comparator to make this a min heap.
+    std::push_heap(tasks_.begin(), tasks_.end(), TaskComparator());
+    return true;
+  }
+
+  // Runs tasks up to the current time. Returns the number of tasks executed.
+  size_t RunTasks() {
+    base::TimeTicks now = clock_->NowTicks();
+    size_t count = 0;
+    while (!tasks_.empty() && tasks_.front().first <= now) {
+      tasks_.front().second.Run();
+      std::pop_heap(tasks_.begin(), tasks_.end(), TaskComparator());
+      tasks_.pop_back();
+      ++count;
+    }
+    return count;
+  }
+
+  // Advances the clock and runs the next task in the queue. Can run more than
+  // one task if multiple tasks have the same scheduled time.
+  size_t RunNextTask() {
+    // Get the time of the next task that can possibly run.
+    base::TimeTicks when = tasks_.front().first;
+
+    // Advance the clock to exactly that time.
+    base::TimeTicks now = clock_->NowTicks();
+    if (now < when) {
+      base::TimeDelta delta = when - now;
+      clock_->Advance(delta);
+    }
+
+    // Run whatever tasks are now eligible to run.
+    return RunTasks();
+  }
+
+  size_t size() const { return tasks_.size(); }
+
+ private:
+  ~TaskRunnerProxy() override {}
+
+  MockTaskRunner* mock_;
+  base::SimpleTestTickClock* clock_;
+
+  // A min-heap of outstanding tasks.
+  using Task = std::pair<base::TimeTicks, base::Closure>;
+  std::vector<Task> tasks_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskRunnerProxy);
+};
+
 enum TestIndicies {
   kSelected,
   kPinned,
@@ -90,12 +182,17 @@ enum TestIndicies {
 };
 }  // namespace
 
-class TabManagerTest : public ChromeRenderViewHostTestHarness {
+class LenientTabManagerTest : public ChromeRenderViewHostTestHarness {
  public:
   WebContents* CreateWebContents() {
     return WebContents::Create(WebContents::CreateParams(profile()));
   }
+
+  MOCK_METHOD2(NotifyRendererProcess,
+               void(const content::RenderProcessHost*,
+                    base::MemoryPressureListener::MemoryPressureLevel));
 };
+using TabManagerTest = testing::StrictMock<LenientTabManagerTest>;
 
 // TODO(georgesak): Add tests for protection to tabs with form input and
 // playing audio;
@@ -336,4 +433,154 @@ TEST_F(TabManagerTest, DiscardedTabKeepsLastActiveTime) {
   EXPECT_TRUE(tabstrip.empty());
 }
 
+namespace {
+
+using MemoryPressureLevel = base::MemoryPressureListener::MemoryPressureLevel;
+
+// Function that always indicates the absence of memory pressure.
+MemoryPressureLevel ReturnNoPressure() {
+  return base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
+}
+
+// Function that simply parrots back an externally specified memory pressure
+// level.
+MemoryPressureLevel ReturnSpecifiedPressure(
+    const MemoryPressureLevel* level) {
+  return *level;
+}
+
+}  // namespace
+
+// Ensure that memory pressure notifications are forwarded to child processes.
+TEST_F(TabManagerTest, ChildProcessNotifications) {
+  TabManager tm;
+
+  // Set up the tab strip.
+  TabStripDummyDelegate delegate;
+  TabStripModel tabstrip(&delegate, profile());
+
+  // Create test clock, task runner.
+  base::SimpleTestTickClock test_clock;
+  MockTaskRunner mock_task_runner;
+  scoped_refptr<TaskRunnerProxy> task_runner(
+      new TaskRunnerProxy(&mock_task_runner, &test_clock));
+
+  // Configure the TabManager for testing.
+  tabstrip.AddObserver(&tm);
+  tm.test_tab_strip_models_.push_back(
+      TabManager::TestTabStripModel(&tabstrip, false /* !is_app */));
+  tm.test_tick_clock_ = &test_clock;
+  tm.task_runner_ = task_runner;
+  tm.notify_renderer_process_ = base::Bind(
+      &TabManagerTest::NotifyRendererProcess, base::Unretained(this));
+
+  // Create two dummy tabs.
+  auto tab1 = CreateWebContents();
+  auto tab2 = CreateWebContents();
+  tabstrip.AppendWebContents(tab1, true);   // Foreground tab.
+  tabstrip.AppendWebContents(tab2, false);  // Opened in background.
+  const content::RenderProcessHost* renderer1 = tab1->GetRenderProcessHost();
+  const content::RenderProcessHost* renderer2 = tab2->GetRenderProcessHost();
+
+  // Expect that the tab manager has not yet encountered memory pressure.
+  EXPECT_FALSE(tm.under_memory_pressure_);
+  EXPECT_EQ(0u, tm.notified_renderers_.size());
+
+  // Simulate a memory pressure situation that will immediately end. This should
+  // cause no notifications or scheduled tasks.
+  auto level = base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE;
+  tm.get_current_pressure_level_ = base::Bind(&ReturnNoPressure);
+  tm.OnMemoryPressure(level);
+  testing::Mock::VerifyAndClearExpectations(&mock_task_runner);
+  EXPECT_FALSE(tm.under_memory_pressure_);
+  EXPECT_EQ(0u, task_runner->size());
+  EXPECT_EQ(0u, tm.notified_renderers_.size());
+
+  // START OF MEMORY PRESSURE
+
+  // Simulate a memory pressure situation that persists. This should cause a
+  // task to be scheduled.
+  tm.get_current_pressure_level_ = base::Bind(
+      &ReturnSpecifiedPressure, base::Unretained(&level));
+  EXPECT_CALL(mock_task_runner, PostDelayedTask(
+      testing::_,
+      testing::_,
+      base::TimeDelta::FromSeconds(tm.kRendererNotificationDelayInSeconds)));
+  EXPECT_CALL(*this, NotifyRendererProcess(renderer2, level));
+  tm.OnMemoryPressure(level);
+  testing::Mock::VerifyAndClearExpectations(&mock_task_runner);
+  testing::Mock::VerifyAndClearExpectations(this);
+  EXPECT_TRUE(tm.under_memory_pressure_);
+  EXPECT_EQ(1u, task_runner->size());
+  EXPECT_EQ(1u, tm.notified_renderers_.size());
+  EXPECT_EQ(1u, tm.notified_renderers_.count(renderer2));
+
+  // REPEATED MEMORY PRESSURE SIGNAL
+
+  // Simulate another memory pressure event. This should not cause any
+  // additional tasks to be scheduled, nor any further renderer notifications.
+  tm.OnMemoryPressure(level);
+  testing::Mock::VerifyAndClearExpectations(&mock_task_runner);
+  testing::Mock::VerifyAndClearExpectations(this);
+  EXPECT_TRUE(tm.under_memory_pressure_);
+  EXPECT_EQ(1u, task_runner->size());
+  EXPECT_EQ(1u, tm.notified_renderers_.size());
+
+  // FIRST SCHEDULED NOTIFICATION
+
+  // Run the scheduled task. This should cause another notification, but this
+  // time to the foreground tab. It should also cause another scheduled event.
+  EXPECT_CALL(mock_task_runner, PostDelayedTask(
+      testing::_,
+      testing::_,
+      base::TimeDelta::FromSeconds(tm.kRendererNotificationDelayInSeconds)));
+  EXPECT_CALL(*this, NotifyRendererProcess(renderer1, level));
+  EXPECT_EQ(1u, task_runner->RunNextTask());
+  testing::Mock::VerifyAndClearExpectations(&mock_task_runner);
+  testing::Mock::VerifyAndClearExpectations(this);
+  EXPECT_TRUE(tm.under_memory_pressure_);
+  EXPECT_EQ(1u, task_runner->size());
+  EXPECT_EQ(2u, tm.notified_renderers_.size());
+  EXPECT_EQ(1u, tm.notified_renderers_.count(renderer1));
+
+  // SECOND SCHEDULED NOTIFICATION
+
+  // Run the scheduled task. This should cause another notification, to the
+  // background tab. It should also cause another scheduled event.
+  EXPECT_CALL(mock_task_runner, PostDelayedTask(
+      testing::_,
+      testing::_,
+      base::TimeDelta::FromSeconds(tm.kRendererNotificationDelayInSeconds)));
+  EXPECT_CALL(*this, NotifyRendererProcess(renderer2, level));
+  EXPECT_EQ(1u, task_runner->RunNextTask());
+  testing::Mock::VerifyAndClearExpectations(&mock_task_runner);
+  testing::Mock::VerifyAndClearExpectations(this);
+  EXPECT_TRUE(tm.under_memory_pressure_);
+  EXPECT_EQ(1u, task_runner->size());
+  EXPECT_EQ(1u, tm.notified_renderers_.size());
+
+  // Expect that the background tab has been notified. The list of notified
+  // renderers maintained by the TabManager should also have been reset because
+  // the notification logic restarts after all renderers are notified.
+  EXPECT_EQ(1u, tm.notified_renderers_.count(renderer2));
+
+  // END OF MEMORY PRESSURE
+
+  // End the memory pressure condition and run the scheduled event. This should
+  // clean up the various state data. It should not schedule another event nor
+  // fire any notifications.
+  level = base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
+  EXPECT_EQ(1u, task_runner->RunNextTask());
+  testing::Mock::VerifyAndClearExpectations(&mock_task_runner);
+  testing::Mock::VerifyAndClearExpectations(this);
+  EXPECT_FALSE(tm.under_memory_pressure_);
+  EXPECT_EQ(0u, task_runner->size());
+  EXPECT_EQ(0u, tm.notified_renderers_.size());
+
+
+  // Clean up the tabstrip.
+  tabstrip.CloseAllTabs();
+  ASSERT_TRUE(tabstrip.empty());
+}
+
 }  // namespace memory