Only rely on downloading proguard for building our examples

For our continious performance tracking I don't want us to pull down everything on every build (we do clean builds)

R=ager@google.com, zerny@google.com

Bug:
Change-Id: I29e9380979918799708a14ebdd41d08cce61d860

build.gradle

diff --git a/build.gradle b/build.gradle
index 8eb9643..ebebe33 100644
--- a/build.gradle
+++ b/build.gradle
@@ -164,6 +164,16 @@
     }
 }
 
+task downloadProguard {
+    cloudDependencies.each { entry ->
+        entry.value.each { entryFile ->
+            if (entryFile.contains("proguard")) {
+                dependsOn "download_deps_${entry.key}/${entryFile}"
+            }
+        }
+    }
+}
+
 task downloadDeps {
     cloudDependencies.each { entry ->
         entry.value.each { entryFile ->
@@ -362,7 +372,7 @@
 }
 
 task buildExampleJars {
-    dependsOn downloadDeps
+    dependsOn downloadProguard
     def examplesDir = file("src/test/examples")
     def proguardScript = "third_party/proguard/proguard5.2.1/bin/proguard.sh"
     task "compile_examples"(type: JavaCompile) {