docs: Edited phrasing for "orderId is blank with test IAP purchases"

Also added links to the In-app Billing Reference documentation in
areas where the "orderId" field is mentioned.

Bug: 29068371
Change-Id: I457e0074032613b4721b16017642eedd457fe7f1
diff --git a/docs/html/google/play/billing/billing_admin.jd b/docs/html/google/play/billing/billing_admin.jd
index 05f3ad5..292cfcc 100644
--- a/docs/html/google/play/billing/billing_admin.jd
+++ b/docs/html/google/play/billing/billing_admin.jd
@@ -748,10 +748,9 @@
 intent.</p>
 
 <p class="note">
-  <strong>Note:</strong> When a user completes a test purchase, the
-  <code>orderId</code> field remains blank. To track test transactions, use
-  the <code>purchaseToken</code> field instead. For more information about
-  working with test purchases, see <a
+  <strong>Note:</strong> Test purchases don't have an <code>orderId</code>
+  field. To track test transactions, you use the <code>purchaseToken</code>
+  field instead. For more information about working with test purchases, see <a
   href="{@docRoot}google/play/billing/billing_testing.html">Testing In-app
   Billing</a>.
 </p>
@@ -766,14 +765,14 @@
 
 <p>For transactions dated 5 December 2012 or later, Google payments assigns a
 Merchant Order Number (rather than a Google Order Number) and reports the Merchant
-Order Number as the value of <code>orderID</code>. Here's an
+Order Number as the value of <code>orderId</code>. Here's an
 example:</p>
 
 <pre>"orderId" : "GPA.1234-5678-9012-34567"</pre>
 
 <p>For transactions dated previous to 5 December 2012, Google checkout assigned
 a Google Order Number and reported that number as the value of
-<code>orderID</code>. Here's an example of an <code>orderID</code> holding a
+<code>orderId</code>. Here's an example of an <code>orderId</code> holding a
 Google Order Number:</p>
 
 <pre>"orderId" : "556515565155651"</pre>
diff --git a/docs/html/google/play/billing/billing_testing.jd b/docs/html/google/play/billing/billing_testing.jd
index 755f3ff..44b7ad3 100644
--- a/docs/html/google/play/billing/billing_testing.jd
+++ b/docs/html/google/play/billing/billing_testing.jd
@@ -81,8 +81,8 @@
 
 <p>
   Once authorized for testing access, those users can make purchases without
-  being charged. The <code>orderId</code> field for test purchases remains
-  blank, ensuring that there are no actual charges to user accounts.
+  being charged. Test purchases don't have an <code>orderId</code> field, which
+  ensures that there are no actual charges to user accounts.
 </p>
 
 <p class="note">
@@ -127,11 +127,11 @@
 purchase dialog.</p>
 
 <p class="note">
-  <strong>Note:</strong> For test purchases, leave the {@code orderId} field
-  blank. You can use the {@code purchaseToken} field to identify test purchases.
+  <strong>Note:</strong> Test purchases don't have an <code>orderId</code>
+  field. To track test purchases, you use the <code>purchaseToken</code> field
+  instead.
 </p>
 
-
 <h4 id="tp-account">Test purchases and developer account</h4>
 <p>Authorized license test accounts are associated with your developer account
 in Google Play, rather than with a specific APK or package name. Identifying an