[ios] Creates flag to enable Messages only for iOS13

Change-Id: I695b93df9fc6a723f76065891935e979ba48796d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2151970Reviewed-by: Chris Lu <thegreenfrog@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760085}

chrome/browser/flag-metadata.json

@@ -2656,6 +2656,11 @@
     "owners": [ "sczs", "thegreenfrog" ],
     "expiry_milestone": 83
   },
+  {
+    "name": "infobar-ui-reboot-only-ios13",
+    "owners": [ "sczs", "thegreenfrog" ],
+    "expiry_milestone": 84
+  },
   {
     "name": "installable-ink-drop",
     "owners": [ "collinbaker", "pbos" ],

ios/chrome/browser/flags/about_flags.mm

@@ -601,6 +601,10 @@ const flags_ui::FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kEnableAutofillCacheServerCardInfoDescription,
      flags_ui::kOsIos,
      FEATURE_VALUE_TYPE(autofill::features::kAutofillCacheServerCardInfo)},
+    {"infobar-ui-reboot-only-ios13",
+     flag_descriptions::kInfobarUIRebootOnlyiOS13Name,
+     flag_descriptions::kInfobarUIRebootOnlyiOS13Description, flags_ui::kOsIos,
+     FEATURE_VALUE_TYPE(kInfobarUIRebootOnlyiOS13)},
 };
 
 // Add all switches from experimental flags to |command_line|.

ios/chrome/browser/flags/ios_chrome_flag_descriptions.cc

@@ -266,6 +266,10 @@ const char kInfobarUIRebootName[] = "Infobar UI Reboot";
 const char kInfobarUIRebootDescription[] =
     "When enabled, Infobar will use the new UI.";
 
+const char kInfobarUIRebootOnlyiOS13Name[] = "Infobar UI Reboot iOS13";
+const char kInfobarUIRebootOnlyiOS13Description[] =
+    "When enabled, Infobar will use the new UI only on iOS13";
+
 const char kInProductHelpDemoModeName[] = "In-Product Help Demo Mode";
 const char kInProductHelpDemoModeDescription[] =
     "When enabled, in-product help promotions occur exactly once per cold "

ios/chrome/browser/flags/ios_chrome_flag_descriptions.h

@@ -226,6 +226,11 @@ extern const char kInfobarOverlayUIDescription[];
 extern const char kInfobarUIRebootName[];
 extern const char kInfobarUIRebootDescription[];
 
+// Title and description for the flag to enable the new UI Reboot on Infobars
+// only on iOS13.
+extern const char kInfobarUIRebootOnlyiOS13Name[];
+extern const char kInfobarUIRebootOnlyiOS13Description[];
+
 // Title and description for the flag to enable feature_engagement::Tracker
 // demo mode.
 extern const char kInProductHelpDemoModeName[];

ios/chrome/browser/ui/infobars/infobar_feature.h

@@ -44,6 +44,11 @@ extern const base::Feature kSaveCardInfobarMessagesUI;
 // Use IsTranslateInfobarMessagesUIEnabled() instead of this constant directly.
 extern const base::Feature kTranslateInfobarMessagesUI;
 
+// Feature to choose whether to use the new Messages Infobar design on iOS13, or
+// the legacy one.
+// Use IsInfobarUIRebootEnabled() instead of this constant directly.
+extern const base::Feature kInfobarUIRebootOnlyiOS13;
+
 // Whether the Messages Infobar UI is enabled. Prefer to use this method instead
 // of kIOSInfobarUIReboot directly.
 bool IsInfobarUIRebootEnabled();

ios/chrome/browser/ui/infobars/infobar_feature.mm

@@ -37,12 +37,22 @@ const base::Feature kSaveCardInfobarMessagesUI{
 // Feature enabled by default since it will always be guarded with
 // |kIOSInfobarUIReboot|, meaning that if necessary,
 // |kTranslateInfobarMessagesUI| can be used as a kill switch.
-// TODO(crbug.com/1014959): Enabled flag once feature is ready.
 const base::Feature kTranslateInfobarMessagesUI{
     "TranslateInfobarMessagesUI", base::FEATURE_ENABLED_BY_DEFAULT};
 
+const base::Feature kInfobarUIRebootOnlyiOS13{
+    "InfobarUIRebootOnlyiOS13", base::FEATURE_DISABLED_BY_DEFAULT};
+
 bool IsInfobarUIRebootEnabled() {
-  return base::FeatureList::IsEnabled(kIOSInfobarUIReboot);
+  if (base::FeatureList::IsEnabled(kInfobarUIRebootOnlyiOS13)) {
+    if (@available(iOS 13, *)) {
+      return base::FeatureList::IsEnabled(kIOSInfobarUIReboot);
+    } else {
+      return NO;
+    }
+  } else {
+    return base::FeatureList::IsEnabled(kIOSInfobarUIReboot);
+  }
 }
 
 bool IsInfobarOverlayUIEnabled() {