Fix typo

Design doc:
https://docs.google.com/document/d/1izV4uC-tiRJG3JLooqY3YRLU22tYOsLTNq0P_InPJeE

To test:
1) Install BobPay.apk from
https://drive.google.com/a/google.com/file/d/0B3ISiXgGE1MNc1FCNlZkN3FMMWs/view?usp=sharing
2) Enable chrome://flags/#android-payment-apps.
3) Navigate to https://rsolomakhin.github.io/pr/bob/.
4) Click "Buy" button on the webpage.

BUG=707246

Review-Url: https://codereview.chromium.org/2807733002
Cr-Commit-Position: refs/heads/master@{#462976}

chrome/android/java/src/org/chromium/chrome/browser/payments/AndroidPaymentAppFinder.java

@@ -60,7 +60,7 @@ public class AndroidPaymentAppFinder implements ManifestVerifyCallback {
      * Meta data name of an app's supported default payment method name.
      */
     static final String META_DATA_NAME_OF_DEFAULT_PAYMENT_METHOD_NAME =
-            "org.chromum.default_payment_method_name";
+            "org.chromium.default_payment_method_name";
 
     /** The maximum number of payment method manifests to download. */
     private static final int MAX_NUMBER_OF_MANIFESTS = 10;