Upgrade gitiles to 0.2-8

Following the upgrade of soy to 2019-03-11 (change I9bf2bdb56), we
also need to upgrade gitiles (specifically gitiles-servlet) to a
release that uses the same version of soy. Using gitiles-servlet
with an older version of soy causes server startup to fail due to
usage of unsupported SoyDoc parameters.

While we're in there, also factor out the artifact repository to a
variable and reuse it for both gitiles artifacts. This saves some
typing when testing locally deployed versions.

Bug: Issue 10771
Change-Id: Idbbca5a7655ba3c515ab919033552975773a6765
diff --git a/WORKSPACE b/WORKSPACE
index 8be67bc..746364f 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -703,21 +703,23 @@
     sha1 = "f7be08ec23c21485b9b5a1cf1654c2ec8c58168d",
 )
 
-GITILES_VERS = "0.2-7"
+GITILES_VERS = "0.2-8"
+
+GITILES_REPO = GERRIT
 
 maven_jar(
     name = "blame-cache",
     artifact = "com.google.gitiles:blame-cache:" + GITILES_VERS,
     attach_source = False,
-    repository = GERRIT,
-    sha1 = "8170f33b8b1db6f55e41d7069fa050a4d102a62b",
+    repository = GITILES_REPO,
+    sha1 = "714fd1d98d02cd8898532ef5169f7b23125747d6",
 )
 
 maven_jar(
     name = "gitiles-servlet",
     artifact = "com.google.gitiles:gitiles-servlet:" + GITILES_VERS,
-    repository = GERRIT,
-    sha1 = "f23b22cb27fe5c4a78f761492082159d17873f57",
+    repository = GITILES_REPO,
+    sha1 = "a416e4ac5a0cad04410440d0b2785fa966bc5a0c",
 )
 
 # prettify must match the version used in Gitiles