Add chrome://flags entry for BlockTabUnders on Android

The UI is not implemented yet on desktop.

Bug: 661629
Change-Id: Iee0b2134d02eb63325b20376c38500a38d49fb9a
Reviewed-on: https://chromium-review.googlesource.com/701474Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506616}

chrome/browser/about_flags.cc

@@ -31,6 +31,7 @@
 #include "chrome/browser/predictors/loading_predictor_config.h"
 #include "chrome/browser/predictors/resource_prefetch_common.h"
 #include "chrome/browser/prerender/prerender_field_trial.h"
+#include "chrome/browser/ui/blocked_content/tab_under_navigation_throttle.h"
 #include "chrome/common/channel_info.h"
 #include "chrome/common/chrome_content_client.h"
 #include "chrome/common/chrome_features.h"
@@ -3545,6 +3546,14 @@ const FeatureEntry kFeatureEntries[] = {
      FEATURE_VALUE_TYPE(features::kDownloadsForeground)},
 #endif  // defined(OS_ANDROID)
 
+#if defined(OS_ANDROID)
+    // TODO(csharrison): Make this available on all platforms when the desktop
+    // UI is finished.
+    {"enable-block-tab-unders", flag_descriptions::kBlockTabUndersName,
+     flag_descriptions::kBlockTabUndersDescription, kOsAndroid,
+     FEATURE_VALUE_TYPE(TabUnderNavigationThrottle::kBlockTabUnders)},
+#endif  // defined(OS_ANDROID)
+
     // NOTE: Adding a new flag requires adding a corresponding entry to enum
     // "LoginCustomFlags" in tools/metrics/histograms/enums.xml. See "Flag
     // Histograms" in tools/metrics/histograms/README.md (run the

chrome/browser/flag_descriptions.cc

@@ -67,6 +67,11 @@ const char kBleAdvertisingInExtensionsDescription[] =
     "Enables BLE Advertising in Chrome Apps. BLE Advertising might interfere "
     "with regular use of Bluetooth Low Energy features.";
 
+const char kBlockTabUndersName[] = "Block tab-unders";
+const char kBlockTabUndersDescription[] =
+    "Blocks tab-unders in Chrome with some native UI to allow the user to "
+    "proceed.";
+
 const char kBrowserSideNavigationName[] = "Enable browser side navigation";
 const char kBrowserSideNavigationDescription[] =
     "Enable browser side navigation (aka PlzNavigate).";

chrome/browser/flag_descriptions.h

@@ -69,6 +69,9 @@ extern const char kBackgroundVideoTrackOptimizationDescription[];
 extern const char kBleAdvertisingInExtensionsName[];
 extern const char kBleAdvertisingInExtensionsDescription[];
 
+extern const char kBlockTabUndersName[];
+extern const char kBlockTabUndersDescription[];
+
 extern const char kBrowserSideNavigationName[];
 extern const char kBrowserSideNavigationDescription[];
 

tools/metrics/histograms/enums.xml

@@ -23295,6 +23295,7 @@ from previous Chrome versions.
   <int value="-1913801713"
       label="UploadCrashReportsUsingJobScheduler:disabled"/>
   <int value="-1912999136" label="enable-automatic-password-saving:enabled"/>
+  <int value="-1911316813" label="BlockTabUnders:disabled"/>
   <int value="-1911153473" label="enable-easy-signin"/>
   <int value="-1909356390"
       label="OverlayScrollbarFlashAfterAnyScrollUpdate:enabled"/>
@@ -23466,6 +23467,7 @@ from previous Chrome versions.
   <int value="-1433719718" label="enable-webrtc-stun-origin"/>
   <int value="-1433087548" label="enable-app-install-alerts"/>
   <int value="-1431563697" label="WebPaymentsMethodSectionOrderV2:enabled"/>
+  <int value="-1426817842" label="BlockTabUnders:enabled"/>
   <int value="-1426034869" label="NoCreditCardAbort:enabled"/>
   <int value="-1419788257" label="enable-experimental-hotwording"/>
   <int value="-1416754663" label="enable-mac-views-native-app-windows"/>