[TabManager] Disable memory pressure notifications to foreground renderers.

chrome/browser/memory/tab_manager_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/memory/tab_manager.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 457 matching lines @@
   // 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 tab0 = CreateWebContents();
   auto tab1 = CreateWebContents();
   auto tab2 = CreateWebContents();
-  tabstrip.AppendWebContents(tab1, true);   // Foreground tab.
-  tabstrip.AppendWebContents(tab2, false);  // Opened in background.
+  tabstrip.AppendWebContents(tab0, true);   // Foreground tab.
+  tabstrip.AppendWebContents(tab1, false);  // Background tab.
+  tabstrip.AppendWebContents(tab2, false);  // Background tab.
   const content::RenderProcessHost* renderer1 = tab1->GetRenderProcessHost();
   const content::RenderProcessHost* renderer2 = tab2->GetRenderProcessHost();
 
+  // Make sure that tab2 has a lower priority than tab1 by its access time.
+  test_clock.Advance(base::TimeDelta::FromMilliseconds(1));
+  tab2->SetLastActiveTime(test_clock.NowTicks());
+  test_clock.Advance(base::TimeDelta::FromMilliseconds(1));
+  tab1->SetLastActiveTime(test_clock.NowTicks());
+
   // 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.
+  // task to be scheduled, and a background renderer to be notified.
   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);
@@ skipping 64 matching lines @@
   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