Show custom error message in payments UI.

chrome/android/java/src/org/chromium/chrome/browser/payments/ui/SectionInformation.java

Index: chrome/android/java/src/org/chromium/chrome/browser/payments/ui/SectionInformation.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/payments/ui/SectionInformation.java b/chrome/android/java/src/org/chromium/chrome/browser/payments/ui/SectionInformation.java
index 2718db49cc9a956ede81538b325cbab3ef3828d1..4eaf2f65d8ecc8ef90588686ace9486dc503ba2c 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/payments/ui/SectionInformation.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/payments/ui/SectionInformation.java
@@ -30,6 +30,7 @@ public class SectionInformation {
     @PaymentRequestUI.DataType private final int mDataType;
     private ArrayList<PaymentOption> mItems;
     private int mSelectedItem;
+    public String mErrorMessage;
 
     /**
      * Builds an empty section without selection.
@@ -173,4 +174,14 @@ public class SectionInformation {
         }
         return 0;
     }
+
+    /** @param msg The optional error message to display when the selection is invalid. */
+    public void setErrorMessage(String msg) {
+        mErrorMessage = msg;
+    }
+
+    /** @return The optional error message to display when the selection is invalid. */
+    public String getErrorMessage() {
+        return mErrorMessage;
+    }
 }