Add a variations parameter to control WebAPK renderer launching.

chrome/android/java/src/org/chromium/chrome/browser/webapps/ChromeWebApkHost.java

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/ChromeWebApkHost.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/ChromeWebApkHost.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/ChromeWebApkHost.java
index 7abec8cbc5763734dd9b84621948cb7b3d676c50..39ed7ca494ed82e3e9c418a75ec058c91c5d4129 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/webapps/ChromeWebApkHost.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/ChromeWebApkHost.java
@@ -133,6 +133,12 @@ public class ChromeWebApkHost {
         return sGooglePlayInstallState;
     }
 
+    /* Returns whether launching renderer in WebAPK process is enabled by Chrome. */
+    public static boolean canLaunchRendererInWebApkProcess() {
+        return isEnabled() && LibraryLoader.isInitialized()
+                && nativeCanLaunchRendererInWebApkProcess();
+    }
+
     /**
      * Check the cached value to figure out if the feature is enabled. We have to use the cached
      * value because native library may not yet been loaded.
@@ -179,5 +185,6 @@ public class ChromeWebApkHost {
     }
 
     private static native boolean nativeCanUseGooglePlayToInstallWebApk();
+    private static native boolean nativeCanLaunchRendererInWebApkProcess();
     private static native boolean nativeCanInstallFromUnknownSources();
 }