Enable download resumption by default.

BUG=7648

Review URL: https://codereview.chromium.org/1538933002

Cr-Commit-Position: refs/heads/master@{#366264}

12 files changed, 59 insertions, 72 deletions

diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index fe09246..8c96baa 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -804,7 +804,7 @@ const FeatureEntry kFeatureEntries[] = {
      IDS_FLAGS_DOWNLOAD_RESUMPTION_NAME,
      IDS_FLAGS_DOWNLOAD_RESUMPTION_DESCRIPTION,
      kOsDesktop,
-     SINGLE_VALUE_TYPE(switches::kEnableDownloadResumption)},
+     FEATURE_VALUE_TYPE(features::kDownloadResumption)},
 #if defined(OS_CHROMEOS)
     {"download-notification",
      IDS_FLAGS_DOWNLOAD_NOTIFICATION_NAME,
diff --git a/chrome/browser/download/download_browsertest.cc b/chrome/browser/download/download_browsertest.cc
index e5f6c5d..9e1ffb6 100644
--- a/chrome/browser/download/download_browsertest.cc
+++ b/chrome/browser/download/download_browsertest.cc
@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
+#include "base/feature_list.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
@@ -80,6 +81,7 @@
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/resource_context.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/common/content_features.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/context_menu_params.h"
 #include "content/public/test/browser_test_utils.h"
@@ -407,6 +409,11 @@ class DownloadTest : public InProcessBrowserTest {
   DownloadTest() {}
 
   void SetUpOnMainThread() override {
+    base::FeatureList::ClearInstanceForTesting();
+    scoped_ptr<base::FeatureList> feature_list(new base::FeatureList);
+    feature_list->InitializeFromCommandLine(
+        features::kDownloadResumption.name, std::string());
+    base::FeatureList::SetInstance(std::move(feature_list));
     BrowserThread::PostTask(
         BrowserThread::IO, FROM_HERE,
         base::Bind(&chrome_browser_net::SetUrlRequestMocksEnabled, true));
@@ -844,11 +851,16 @@ class DownloadTest : public InProcessBrowserTest {
         browser()->tab_strip_model()->GetActiveWebContents();
     ASSERT_TRUE(web_contents);
 
-    scoped_ptr<content::DownloadTestObserver> observer(
-        new content::DownloadTestObserverTerminal(
-            download_manager,
-            1,
-            content::DownloadTestObserver::ON_DANGEROUS_DOWNLOAD_FAIL));
+    scoped_ptr<content::DownloadTestObserver> observer;
+    if (download_info.reason == content::DOWNLOAD_INTERRUPT_REASON_NONE) {
+      observer.reset(new content::DownloadTestObserverTerminal(
+          download_manager, 1,
+          content::DownloadTestObserver::ON_DANGEROUS_DOWNLOAD_FAIL));
+    } else {
+      observer.reset(new content::DownloadTestObserverInterrupted(
+          download_manager, 1,
+          content::DownloadTestObserver::ON_DANGEROUS_DOWNLOAD_FAIL));
+    }
 
     if (download_info.download_method == DOWNLOAD_DIRECT) {
       // Go directly to download.  Don't wait for navigation.
@@ -1691,9 +1703,11 @@ IN_PROC_BROWSER_TEST_F(DownloadTest, DownloadHistoryCheck) {
   // at this point as our queries will be behind the history updates
   // invoked by completion.
   scoped_ptr<content::DownloadTestObserver> download_observer(
-      CreateWaiter(browser(), 1));
-  ui_test_utils::NavigateToURL(browser(),
-      GURL(net::URLRequestSlowDownloadJob::kErrorDownloadUrl));
+      new content::DownloadTestObserverInterrupted(
+          DownloadManagerForBrowser(browser()), 1,
+          content::DownloadTestObserver::ON_DANGEROUS_DOWNLOAD_FAIL));
+  ui_test_utils::NavigateToURL(
+      browser(), GURL(net::URLRequestSlowDownloadJob::kErrorDownloadUrl));
   download_observer->WaitForFinished();
   EXPECT_EQ(1u, download_observer->NumDownloadsSeenInState(
       DownloadItem::INTERRUPTED));
@@ -3018,8 +3032,6 @@ IN_PROC_BROWSER_TEST_F(DownloadTest, MAYBE_DownloadTest_PercentComplete) {
 // A download that is interrupted due to a file error should be able to be
 // resumed.
 IN_PROC_BROWSER_TEST_F(DownloadTest, Resumption_NoPrompt) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   scoped_refptr<content::TestFileErrorInjector> error_injector(
       content::TestFileErrorInjector::Create(
           DownloadManagerForBrowser(browser())));
@@ -3043,8 +3055,6 @@ IN_PROC_BROWSER_TEST_F(DownloadTest, Resumption_NoPrompt) {
 // path is invalid or unusable should cause a prompt to be displayed on
 // resumption.
 IN_PROC_BROWSER_TEST_F(DownloadTest, Resumption_WithPrompt) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   scoped_refptr<content::TestFileErrorInjector> error_injector(
       content::TestFileErrorInjector::Create(
           DownloadManagerForBrowser(browser())));
@@ -3067,8 +3077,6 @@ IN_PROC_BROWSER_TEST_F(DownloadTest, Resumption_WithPrompt) {
 // The user shouldn't be prompted on a resumed download unless a prompt is
 // necessary due to the interrupt reason.
 IN_PROC_BROWSER_TEST_F(DownloadTest, Resumption_WithPromptAlways) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   browser()->profile()->GetPrefs()->SetBoolean(
       prefs::kPromptForDownload, true);
   scoped_refptr<content::TestFileErrorInjector> error_injector(
@@ -3097,8 +3105,6 @@ IN_PROC_BROWSER_TEST_F(DownloadTest, Resumption_WithPromptAlways) {
 // A download that is interrupted due to a transient error should be resumed
 // automatically.
 IN_PROC_BROWSER_TEST_F(DownloadTest, Resumption_Automatic) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   scoped_refptr<content::TestFileErrorInjector> error_injector(
       content::TestFileErrorInjector::Create(
           DownloadManagerForBrowser(browser())));
@@ -3117,8 +3123,6 @@ IN_PROC_BROWSER_TEST_F(DownloadTest, Resumption_Automatic) {
 
 // An interrupting download should be resumable multiple times.
 IN_PROC_BROWSER_TEST_F(DownloadTest, Resumption_MultipleAttempts) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   scoped_refptr<content::TestFileErrorInjector> error_injector(
       content::TestFileErrorInjector::Create(
           DownloadManagerForBrowser(browser())));
diff --git a/chrome/browser/download/download_shelf_context_menu.cc b/chrome/browser/download/download_shelf_context_menu.cc
index b541b59..91a5728 100644
--- a/chrome/browser/download/download_shelf_context_menu.cc
+++ b/chrome/browser/download/download_shelf_context_menu.cc
@@ -4,10 +4,9 @@
 
 #include "chrome/browser/download/download_shelf_context_menu.h"
 
-#include "base/command_line.h"
 #include "chrome/browser/download/download_item_model.h"
 #include "chrome/grit/generated_resources.h"
-#include "content/public/common/content_switches.h"
+#include "content/public/common/content_features.h"
 #include "extensions/common/extension.h"
 #include "ui/base/l10n/l10n_util.h"
 
@@ -21,8 +20,7 @@ namespace {
 
 // Returns true if downloads resumption is enabled.
 bool IsDownloadResumptionEnabled() {
-  return base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kEnableDownloadResumption);
+  return base::FeatureList::IsEnabled(features::kDownloadResumption);
 }
 
 }  // namespace
diff --git a/chrome/browser/download/notification/download_notification_browsertest.cc b/chrome/browser/download/notification/download_notification_browsertest.cc
index 7846aea..a04323e 100644
--- a/chrome/browser/download/notification/download_notification_browsertest.cc
+++ b/chrome/browser/download/notification/download_notification_browsertest.cc
@@ -668,7 +668,7 @@ IN_PROC_BROWSER_TEST_F(DownloadNotificationTest, InterruptDownload) {
   // Installs observers before requesting.
   NotificationUpdateObserver
       download_notification_update_observer(notification_id());
-  content::DownloadTestObserverTerminal download_terminal_observer(
+  content::DownloadTestObserverInterrupted download_terminal_observer(
       GetDownloadManager(browser()),
       1u, /* wait_count */
       content::DownloadTestObserver::ON_DANGEROUS_DOWNLOAD_FAIL);
@@ -722,7 +722,7 @@ IN_PROC_BROWSER_TEST_F(DownloadNotificationTest,
 
   // Installs observers before requesting the completion.
   NotificationAddObserver download_notification_add_observer;
-  content::DownloadTestObserverTerminal download_terminal_observer(
+  content::DownloadTestObserverInterrupted download_terminal_observer(
       download_manager,
       1u, /* wait_count */
       content::DownloadTestObserver::ON_DANGEROUS_DOWNLOAD_FAIL);
diff --git a/chrome/browser/extensions/api/downloads/downloads_api_browsertest.cc b/chrome/browser/extensions/api/downloads/downloads_api_browsertest.cc
index 6e8821d..6f78404 100644
--- a/chrome/browser/extensions/api/downloads/downloads_api_browsertest.cc
+++ b/chrome/browser/extensions/api/downloads/downloads_api_browsertest.cc
@@ -37,7 +37,7 @@
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/storage_partition.h"
 #include "content/public/browser/web_contents.h"
-#include "content/public/common/content_switches.h"
+#include "content/public/common/content_features.h"
 #include "content/public/test/download_test_observer.h"
 #include "extensions/browser/event_router.h"
 #include "extensions/browser/notification_types.h"
@@ -309,6 +309,12 @@ class DownloadExtensionTest : public ExtensionApiTest {
 
   // InProcessBrowserTest
   void SetUpOnMainThread() override {
+    base::FeatureList::ClearInstanceForTesting();
+    scoped_ptr<base::FeatureList> feature_list(new base::FeatureList);
+    feature_list->InitializeFromCommandLine(
+        features::kDownloadResumption.name, std::string());
+    base::FeatureList::SetInstance(std::move(feature_list));
+
     ExtensionApiTest::SetUpOnMainThread();
     BrowserThread::PostTask(
         BrowserThread::IO, FROM_HERE,
@@ -3858,8 +3864,6 @@ IN_PROC_BROWSER_TEST_F(
 IN_PROC_BROWSER_TEST_F(
     DownloadExtensionTest,
     MAYBE_DownloadExtensionTest_OnDeterminingFilename_InterruptedResume) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   LoadExtension("downloads_split");
   ASSERT_TRUE(StartEmbeddedTestServer());
   GoOnTheRecord();
diff --git a/content/browser/download/download_browsertest.cc b/content/browser/download/download_browsertest.cc
index 73a21c4..c763b87 100644
--- a/content/browser/download/download_browsertest.cc
+++ b/content/browser/download/download_browsertest.cc
@@ -8,7 +8,7 @@
 #include <vector>
 
 #include "base/callback_helpers.h"
-#include "base/command_line.h"
+#include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
@@ -26,7 +26,7 @@
 #include "content/browser/download/download_resource_handler.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/power_save_blocker.h"
-#include "content/public/common/content_switches.h"
+#include "content/public/common/content_features.h"
 #include "content/public/common/webplugininfo.h"
 #include "content/public/test/browser_test_utils.h"
 #include "content/public/test/content_browser_test.h"
@@ -709,8 +709,12 @@ class DownloadResumptionContentTest
       public ::testing::WithParamInterface<DownloadResumptionTestType> {
  public:
   void SetUpOnMainThread() override {
-    base::CommandLine::ForCurrentProcess()->AppendSwitch(
-        switches::kEnableDownloadResumption);
+    base::FeatureList::ClearInstanceForTesting();
+    scoped_ptr<base::FeatureList> feature_list(new base::FeatureList);
+    feature_list->InitializeFromCommandLine(
+        features::kDownloadResumption.name, std::string());
+    base::FeatureList::SetInstance(std::move(feature_list));
+
     DownloadContentTest::SetUpOnMainThread();
 
     if (GetParam() == DownloadResumptionTestType::RESUME_WITHOUT_RENDERER)
diff --git a/content/browser/download/download_item_impl.cc b/content/browser/download/download_item_impl.cc
index cf42944..2826d31 100644
--- a/content/browser/download/download_item_impl.cc
+++ b/content/browser/download/download_item_impl.cc
@@ -27,7 +27,6 @@
 
 #include "base/basictypes.h"
 #include "base/bind.h"
-#include "base/command_line.h"
 #include "base/files/file_util.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
@@ -49,7 +48,7 @@
 #include "content/public/browser/download_danger_type.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 #include "content/public/browser/download_url_parameters.h"
-#include "content/public/common/content_switches.h"
+#include "content/public/common/content_features.h"
 #include "content/public/common/referrer.h"
 #include "net/base/net_util.h"
 
@@ -93,8 +92,7 @@ static void DownloadFileCancel(scoped_ptr<DownloadFile> download_file) {
 }
 
 bool IsDownloadResumptionEnabled() {
-  return base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kEnableDownloadResumption);
+  return base::FeatureList::IsEnabled(features::kDownloadResumption);
 }
 
 }  // namespace
@@ -1672,12 +1670,7 @@ void DownloadItemImpl::AutoResumeIfValid() {
 
 void DownloadItemImpl::ResumeInterruptedDownload() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
-
-  // If the flag for downloads resumption isn't enabled, ignore
-  // this request.
-  const base::CommandLine& command_line =
-      *base::CommandLine::ForCurrentProcess();
-  if (!command_line.HasSwitch(switches::kEnableDownloadResumption))
+  if (!IsDownloadResumptionEnabled())
     return;
 
   // If we're not interrupted, ignore the request; our caller is drunk.
diff --git a/content/browser/download/download_item_impl_unittest.cc b/content/browser/download/download_item_impl_unittest.cc
index 862d7d8..75fce50 100644
--- a/content/browser/download/download_item_impl_unittest.cc
+++ b/content/browser/download/download_item_impl_unittest.cc
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/callback.h"
-#include "base/command_line.h"
+#include "base/feature_list.h"
 #include "base/message_loop/message_loop.h"
 #include "base/stl_util.h"
 #include "base/threading/thread.h"
@@ -17,7 +17,7 @@
 #include "content/public/browser/download_destination_observer.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 #include "content/public/browser/download_url_parameters.h"
-#include "content/public/common/content_switches.h"
+#include "content/public/common/content_features.h"
 #include "content/public/test/mock_download_item.h"
 #include "content/public/test/test_browser_context.h"
 #include "content/public/test/test_browser_thread.h"
@@ -192,6 +192,11 @@ class DownloadItemTest : public testing::Test {
   }
 
   virtual void SetUp() {
+    base::FeatureList::ClearInstanceForTesting();
+    scoped_ptr<base::FeatureList> feature_list(new base::FeatureList);
+    feature_list->InitializeFromCommandLine(features::kDownloadResumption.name,
+                                            std::string());
+    base::FeatureList::SetInstance(std::move(feature_list));
   }
 
   virtual void TearDown() {
@@ -399,9 +404,6 @@ TEST_F(DownloadItemTest, NotificationAfterDestroyed) {
 }
 
 TEST_F(DownloadItemTest, ContinueAfterInterrupted) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
-
   TestBrowserContext test_browser_context;
   DownloadItemImpl* item = CreateDownloadItem();
   TestDownloadItemObserver observer(item);
@@ -432,9 +434,6 @@ TEST_F(DownloadItemTest, ContinueAfterInterrupted) {
 
 // Same as above, but with a non-continuable interrupt.
 TEST_F(DownloadItemTest, RestartAfterInterrupted) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
-
   DownloadItemImpl* item = CreateDownloadItem();
   TestDownloadItemObserver observer(item);
   MockDownloadFile* download_file =
@@ -455,9 +454,6 @@ TEST_F(DownloadItemTest, RestartAfterInterrupted) {
 
 // Check we do correct cleanup for RESUME_MODE_INVALID interrupts.
 TEST_F(DownloadItemTest, UnresumableInterrupt) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
-
   DownloadItemImpl* item = CreateDownloadItem();
   TestDownloadItemObserver observer(item);
   MockDownloadFile* download_file =
@@ -484,9 +480,6 @@ TEST_F(DownloadItemTest, UnresumableInterrupt) {
 }
 
 TEST_F(DownloadItemTest, LimitRestartsAfterInterrupted) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
-
   TestBrowserContext test_browser_context;
   DownloadItemImpl* item = CreateDownloadItem();
   base::WeakPtr<DownloadDestinationObserver> as_observer(
@@ -546,9 +539,6 @@ TEST_F(DownloadItemTest, LimitRestartsAfterInterrupted) {
 
 // Test that resumption uses the final URL in a URL chain when resuming.
 TEST_F(DownloadItemTest, ResumeUsingFinalURL) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
-
   TestBrowserContext test_browser_context;
   scoped_ptr<DownloadCreateInfo> create_info(new DownloadCreateInfo);
   create_info->save_info = scoped_ptr<DownloadSaveInfo>(new DownloadSaveInfo());
@@ -847,8 +837,6 @@ TEST_F(DownloadItemTest, InterruptedBeforeIntermediateRename_Restart) {
 // intermediate path should be retained when the download is interrupted after
 // the intermediate rename succeeds.
 TEST_F(DownloadItemTest, InterruptedBeforeIntermediateRename_Continue) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   DownloadItemImpl* item = CreateDownloadItem();
   DownloadItemImplDelegate::DownloadTargetCallback callback;
   MockDownloadFile* download_file =
@@ -882,8 +870,6 @@ TEST_F(DownloadItemTest, InterruptedBeforeIntermediateRename_Continue) {
 // As above. If the intermediate rename fails, then the interrupt reason should
 // be set to the destination error and the intermediate path should be empty.
 TEST_F(DownloadItemTest, InterruptedBeforeIntermediateRename_Failed) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   DownloadItemImpl* item = CreateDownloadItem();
   DownloadItemImplDelegate::DownloadTargetCallback callback;
   MockDownloadFile* download_file =
@@ -1282,8 +1268,6 @@ TEST_F(DownloadItemTest, StealDangerousDownload) {
 }
 
 TEST_F(DownloadItemTest, StealInterruptedDangerousDownload) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   base::FilePath returned_path;
   DownloadItemImpl* item = CreateDownloadItem();
   MockDownloadFile* download_file =
@@ -1308,8 +1292,6 @@ TEST_F(DownloadItemTest, StealInterruptedDangerousDownload) {
 }
 
 TEST_F(DownloadItemTest, StealInterruptedNonResumableDangerousDownload) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableDownloadResumption);
   base::FilePath returned_path;
   DownloadItemImpl* item = CreateDownloadItem();
   MockDownloadFile* download_file =
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index fef006d..a9e9acf 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -8,6 +8,11 @@ namespace features {
 
 // All features in alphabetical order.
 
+// Downloads resumption will be controllable via a flag until it's enabled
+// permanently. See https://crbug.com/7648
+const base::Feature kDownloadResumption{"DownloadResumption",
+                                        base::FEATURE_ENABLED_BY_DEFAULT};
+
 // The Experimental Framework for controlling access to API experiments.
 const base::Feature kExperimentalFramework{"ExperimentalFramework",
                                            base::FEATURE_DISABLED_BY_DEFAULT};
diff --git a/content/public/common/content_features.h b/content/public/common/content_features.h
index 3abb36b..0645a2e 100644
--- a/content/public/common/content_features.h
+++ b/content/public/common/content_features.h
@@ -8,14 +8,15 @@
 #ifndef CONTENT_PUBLIC_COMMON_CONTENT_FEATURES_H_
 #define CONTENT_PUBLIC_COMMON_CONTENT_FEATURES_H_
 
-#include "build/build_config.h"
 #include "base/feature_list.h"
+#include "build/build_config.h"
 #include "content/common/content_export.h"
 
 namespace features {
 
 // All features in alphabetical order. The features should be documented
 // alongside the definition of their values in the .cc file.
+CONTENT_EXPORT extern const base::Feature kDownloadResumption;
 CONTENT_EXPORT extern const base::Feature kExperimentalFramework;
 
 #if defined(OS_ANDROID)
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 2399fe5..ceb611e 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -337,9 +337,6 @@ const char kEnableDisplayList2dCanvas[]     = "enable-display-list-2d-canvas";
 const char kForceDisplayList2dCanvas[]      = "force-display-list-2d-canvas";
 const char kDisableDisplayList2dCanvas[]    = "disable-display-list-2d-canvas";
 
-// Enables restarting interrupted downloads.
-const char kEnableDownloadResumption[]      = "enable-download-resumption";
-
 // Disables (unprefixed) Encrypted Media Extensions.
 const char kDisableEncryptedMedia[] = "disable-encrypted-media";
 
diff --git a/content/public/common/content_switches.h b/content/public/common/content_switches.h
index 168ed4b..3c9954f 100644
--- a/content/public/common/content_switches.h
+++ b/content/public/common/content_switches.h
@@ -104,7 +104,6 @@ CONTENT_EXPORT extern const char kEnableBlinkFeatures[];
 CONTENT_EXPORT extern const char kEnableBrowserSideNavigation[];
 CONTENT_EXPORT extern const char kEnableDisplayList2dCanvas[];
 CONTENT_EXPORT extern const char kEnableDistanceFieldText[];
-CONTENT_EXPORT extern const char kEnableDownloadResumption[];
 CONTENT_EXPORT extern const char kEnableExperimentalCanvasFeatures[];
 CONTENT_EXPORT extern const char kEnableExperimentalWebPlatformFeatures[];
 CONTENT_EXPORT extern const char kEnableFeatures[];