Docs: Update 5.1 CTS downloads to R4

Bug:25597685
Change-Id: I6f60517df7422502722ab4aab00d3e4b38949c63
diff --git a/src/compatibility/downloads.jd b/src/compatibility/downloads.jd
index 9eb072a..117ece0 100644
--- a/src/compatibility/downloads.jd
+++ b/src/compatibility/downloads.jd
@@ -51,22 +51,22 @@
 <h2 id="android-51">Android 5.1</h2>
 <p>Android 5.1 is the release of the development milestone code-named Lollipop-MR1.
 The source code for the following tests can be synced with the
-'android-cts-5.1_r3' tag in the open source tree.</p>
+'android-cts-5.1_r4' tag in the open source tree.</p>
 <ul>
 <li><a href="5.1/android-5.1-cdd.pdf">Android 5.1 Compatibility Definition
 Document (CDD)</a></li>
 <li><a
-href="https://dl.google.com/dl/android/cts/android-cts-5.1_r3-linux_x86-arm.zip">Android
-5.1 R3 Compatibility Test Suite (CTS) - ARM</a></li>
+href="https://dl.google.com/dl/android/cts/android-cts-5.1_r4-linux_x86-arm.zip">Android
+5.1 R4 Compatibility Test Suite (CTS) - ARM</a></li>
 <li><a
-href="https://dl.google.com/dl/android/cts/android-cts-5.1_r3-linux_x86-x86.zip">Android
-5.1 R3 Compatibility Test Suite (CTS) - x86</a></li>
+href="https://dl.google.com/dl/android/cts/android-cts-5.1_r4-linux_x86-x86.zip">Android
+5.1 R4 Compatibility Test Suite (CTS) - x86</a></li>
 <li><a
-href="https://dl.google.com/dl/android/cts/android-cts-verifier-5.1_r3-linux_x86-arm.zip">Android
-5.1 R3 CTS Verifier - ARM</a></li>
+href="https://dl.google.com/dl/android/cts/android-cts-verifier-5.1_r4-linux_x86-arm.zip">Android
+5.1 R4 CTS Verifier - ARM</a></li>
 <li><a
-href="https://dl.google.com/dl/android/cts/android-cts-verifier-5.1_r3-linux_x86-x86.zip">Android
-5.1 R3 CTS Verifier - x86</a></li>
+href="https://dl.google.com/dl/android/cts/android-cts-verifier-5.1_r4-linux_x86-x86.zip">Android
+5.1 R4 CTS Verifier - x86</a></li>
 </ul>
 
 <h2 id="android-50">Android 5.0</h2>