Finch kill switch feature for background tab.

chrome/android/java/src/org/chromium/chrome/browser/ChromeFeatureList.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ChromeFeatureList.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ChromeFeatureList.java b/chrome/android/java/src/org/chromium/chrome/browser/ChromeFeatureList.java
index 36e7daaff2ed378726ba17a95521522c64eb956c..ca32f65496120c2cd36bc0186cae5d0c804632ec 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ChromeFeatureList.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ChromeFeatureList.java
@@ -63,8 +63,10 @@ public abstract class ChromeFeatureList {
     public static boolean isEnabled(String featureName) {
         if (sTestFeatures != null) {
             Boolean enabled = sTestFeatures.get(featureName);
-            if (enabled == null) throw new IllegalArgumentException(featureName);
-            return enabled.booleanValue();
+            if (enabled != null) {
+                return enabled.booleanValue();
+            }
+            // Otherwise fall through to a native call.
         }
 
         assert isInitialized();
@@ -147,6 +149,7 @@ public abstract class ChromeFeatureList {
     public static final String ANDROID_PAYMENT_APPS = "AndroidPaymentApps";
     public static final String ANDROID_PAYMENT_APPS_FILTER = "AndroidPaymentAppsFilter";
     public static final String AUTOFILL_SCAN_CARDHOLDER_NAME = "AutofillScanCardholderName";
+    public static final String CCT_BACKGROUND_TAB = "CCTBackgroundTab";
     public static final String CCT_EXTERNAL_LINK_HANDLING = "CCTExternalLinkHandling";
     public static final String CCT_POST_MESSAGE_API = "CCTPostMessageAPI";
     public static final String CHROME_HOME = "ChromeHome";