[ios] Add experimental flag to disable the DCheckIsFatal feature.

Change-Id: Ibf2479334f25f993c8b683144d766ccd07291714
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1860520Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709514}

ios/chrome/browser/flags/about_flags.mm

@@ -653,6 +653,19 @@ void ConvertFlagsToSwitches(flags_ui::FlagsStorage* flags_storage,
 std::vector<std::string> RegisterAllFeatureVariationParameters(
     flags_ui::FlagsStorage* flags_storage,
     base::FeatureList* feature_list) {
+  // Occasionally DCHECK crashes on canary can be very distuptive.  An
+  // experimental flag was added to aid in temporarily disabling this for
+  // canary testers.
+#if defined(DCHECK_IS_CONFIGURABLE)
+  if (experimental_flags::AreDCHECKCrashesDisabled()) {
+    std::vector<base::FeatureList::FeatureOverrideInfo> overrides;
+    overrides.push_back(
+        {std::cref(base::kDCheckIsFatalFeature),
+         base::FeatureList::OverrideState::OVERRIDE_DISABLE_FEATURE});
+    feature_list->RegisterExtraFeatureOverrides(std::move(overrides));
+  }
+#endif  // defined(DCHECK_IS_CONFIGURABLE)
+
   return GetGlobalFlagsState().RegisterAllFeatureVariationParameters(
       flags_storage, feature_list);
 }

ios/chrome/browser/resources/Settings.bundle/Experimental.plist

@@ -98,6 +98,16 @@
 			<key>DefaultValue</key>
 			<false/>
 		</dict>
+		<dict>
+			<key>Type</key>
+			<string>PSToggleSwitchSpecifier</string>
+			<key>Title</key>
+			<string>Disable DCHECK Crashes</string>
+			<key>Key</key>
+			<string>DisableDCHECKCrashes</string>
+			<key>DefaultValue</key>
+			<false/>
+		</dict>
 		<dict>
 			<key>Type</key>
 			<string>PSToggleSwitchSpecifier</string>

ios/chrome/browser/system_flags.h

@@ -57,6 +57,9 @@ bool IsThirdPartyKeyboardWorkaroundEnabled();
 // only once.
 bool MustClearApplicationGroupSandbox();
 
+// Whether the DCheckIsFatal feature should be disabled.
+bool AreDCHECKCrashesDisabled();
+
 }  // namespace experimental_flags
 
 #endif  // IOS_CHROME_BROWSER_SYSTEM_FLAGS_H_

ios/chrome/browser/system_flags.mm

@@ -34,6 +34,7 @@
 
 namespace {
 
+NSString* const kDisableDCHECKCrashes = @"DisableDCHECKCrashes";
 NSString* const kEnableStartupCrash = @"EnableStartupCrash";
 NSString* const kFirstRunForceEnabled = @"FirstRunForceEnabled";
 NSString* const kGaiaEnvironment = @"GAIAEnvironment";
@@ -96,6 +97,11 @@ bool IsStartupCrashEnabled() {
   return [[NSUserDefaults standardUserDefaults] boolForKey:kEnableStartupCrash];
 }
 
+bool AreDCHECKCrashesDisabled() {
+  return
+      [[NSUserDefaults standardUserDefaults] boolForKey:kDisableDCHECKCrashes];
+}
+
 bool MustClearApplicationGroupSandbox() {
   bool value =
       [[NSUserDefaults standardUserDefaults] boolForKey:kClearApplicationGroup];