ui/base: Enable ui_java dep in the GN version ui_base target.

ui_java target was ported in
https://chromium.googlesource.com/chromium/src/+/26046b5fe46738a9c214a64862831e9417f27850
by cjhopman.

This patch was tested with the following command lines:

$ out/Debug/gn gen out_gn/Debug/ --args='os="android" cpu_arch="arm"'

$ ninja -C out_gn/Debug/ ui/base

BUG=None
TEST=see above
TBR=sky@chromium.org,brettw@chromium.org

Review URL: https://codereview.chromium.org/819233002

Cr-Commit-Position: refs/heads/master@{#309510}

ui/base/BUILD.gn

@@ -641,10 +641,7 @@ component("base") {
   }
 
   if (is_android && is_android_webview_build) {
-    deps += [
-      #TODO(GYP): port this component to GN.
-      #"//ui/android:ui_java",
-    ]
+    deps += [ "//ui/android:ui_java" ]
   }
 
   if (is_android && !use_aura) {