Android: Add comment for TemplateUrlService dep

PrefServiceBridge is not intrinsically coupled with TemplateUrlService.
Add comment that this was load-bearing at one point but should be moved
during TemplateUrlService refactor.

Bug: 967695
Change-Id: I3c76cc77335246d16ddb2ce3528f0e2a06006aed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1632412
Commit-Queue: Peter Wen <wnwen@chromium.org>
Commit-Queue: Yaron Friedman <yfriedman@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Auto-Submit: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664313}

chrome/android/java/src/org/chromium/chrome/browser/preferences/PrefServiceBridge.java

@@ -97,6 +97,8 @@ public class PrefServiceBridge {
         if (sInstance == null) {
             sInstance = new PrefServiceBridge();
 
+            // TODO(wnwen): Check while refactoring TemplateUrlService whether this belongs here.
+            // This is necessary as far as ensuring that TemplateUrlService is loaded at some point.
             // Put initialization here to make instantiation in unit tests easier.
             TemplateUrlService.getInstance().load();
         }