Add Gmail 180826.15

Change-Id: I51178790a90f8f81999f41a13eecb73ae039c5cd
diff --git a/build.gradle b/build.gradle
index 06a0632..2276798 100644
--- a/build.gradle
+++ b/build.gradle
@@ -329,6 +329,7 @@
 def x20Dependencies = [
     "third_party": [
         "gmail/gmail_android_170604.16",
+        "gmail/gmail_android_180826.15",
         "chrome",
         "gmscore/v4",
         "gmscore/v5",