Upstream: Initialize ChromeWebApkHost in WebappLaunchActivity.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappLauncherActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappLauncherActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappLauncherActivity.java
index 8a624c4a4d943d3180def2308c5b20859de6c62f..0ef89067e72128f3329f15840d6274b2c5c3692c 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappLauncherActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappLauncherActivity.java
@@ -64,6 +64,9 @@ public class WebappLauncherActivity extends Activity {
             // - the request was for a WebAPK that is valid;
             // - the MAC is present and valid for the homescreen shortcut to be opened;
             // - the intent was sent by Chrome.
+            if (CommandLine.getInstance().hasSwitch(ChromeSwitches.ENABLE_WEBAPK)) {
+                ChromeWebApkHost.init();
+            }
             boolean isValidWebApk = isValidWebApk(webApkPackageName, webappUrl);
 
             if (isValidWebApk