[TabManager] Enable tab discarding by default.

This CL enables tab discarding by default and keeps the existing feature only as a kill switch. BUG=551995 Review-Url: https://codereview.chromium.org/2373653002 Cr-Commit-Position: refs/heads/master@{#421178}
cbchan · Sep 27, 2016 · ea47d44 · ea47d44
1 parent 6a45441
commit ea47d44
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Showing 4 changed files with 8 additions and 14 deletions.
diff --git a/chrome/browser/memory/tab_manager.cc b/chrome/browser/memory/tab_manager.cc
@@ -135,6 +135,7 @@ TabManager::TabManager()
     : discard_count_(0),
       recent_tab_discard_(false),
       discard_once_(false),
+      minimum_protection_time_(base::TimeDelta::FromMinutes(10)),
       browser_tab_strip_tracker_(this, nullptr, nullptr),
       test_tick_clock_(nullptr),
       under_memory_pressure_(false),
@@ -157,12 +158,15 @@ TabManager::~TabManager() {
 
 void TabManager::Start() {
 #if defined(OS_WIN) || defined(OS_MACOSX)
-  // If the feature is not enabled, do nothing.
+  // Note that discarding is now enabled by default. This check is kept as a
+  // kill switch.
+  // TODO(georgesak): remote this when deemed not needed anymore.
   if (!base::FeatureList::IsEnabled(features::kAutomaticTabDiscarding))
     return;
 
   // Check the variation parameter to see if a tab is to be protected for an
-  // amount of time after being backgrounded. The value is in seconds.
+  // amount of time after being backgrounded. The value is in seconds. Default
+  // is 10 minutes if the variation is absent.
   std::string minimum_protection_time_string =
       variations::GetVariationParamValue(features::kAutomaticTabDiscarding.name,
                                          "MinimumProtectionTime");

diff --git a/chrome/browser/memory/tab_manager_browsertest.cc b/chrome/browser/memory/tab_manager_browsertest.cc
@@ -33,16 +33,6 @@ using content::OpenURLParams;
 namespace memory {
 
 class TabManagerTest : public InProcessBrowserTest {
- public:
-  // Tab discarding is enabled by default on CrOS. On other platforms, force it
-  // by turning on the corresponding experiment as some tests assume this
-  // behavior it turned on.
-  void SetUpCommandLine(base::CommandLine* command_line) override {
-#if !defined(OS_LINUX)
-    command_line->AppendSwitchASCII(switches::kEnableFeatures,
-                                    features::kAutomaticTabDiscarding.name);
-#endif
-  }
 };
 
 IN_PROC_BROWSER_TEST_F(TabManagerTest, TabManagerBasics) {

diff --git a/chrome/browser/memory/tab_manager_unittest.cc b/chrome/browser/memory/tab_manager_unittest.cc
@@ -451,7 +451,7 @@ TEST_F(TabManagerTest, DiscardedTabKeepsLastActiveTime) {
 
 // Test to see if a tab can only be discarded once. On Windows and Mac, this
 // defaults to true unless overridden through a variation parameter. On other
-// platforms, it's always false
+// platforms, it's always false.
 #if defined(OS_WIN) || defined(OS_MACOSX)
 TEST_F(TabManagerTest, CanOnlyDiscardOnce) {
   TabManager tab_manager;

diff --git a/chrome/common/chrome_features.cc b/chrome/common/chrome_features.cc
@@ -17,7 +17,7 @@ const base::Feature kArcMemoryManagement{
 #if defined(OS_WIN) || defined(OS_MACOSX)
 // Enables automatic tab discarding, when the system is in low memory state.
 const base::Feature kAutomaticTabDiscarding{"AutomaticTabDiscarding",
-                                            base::FEATURE_DISABLED_BY_DEFAULT};
+                                            base::FEATURE_ENABLED_BY_DEFAULT};
 #endif  // defined(OS_WIN) || defined(OS_MACOSX)
 
 #if defined(OS_WIN) || defined(OS_LINUX)