Disallow shadowed variables in content layer.

Prevent shadowed variables in use on the content layer.

BUG=794619

Change-Id: I88a4d85565e47e58aba20b16be8b6f7533290bc3
Reviewed-on: https://chromium-review.googlesource.com/927181
Reviewed-by: Avi Drissman <[email protected]>
Commit-Queue: Dave Tapuska <[email protected]>
Cr-Commit-Position: refs/heads/master@{#538560}
diff --git a/content/BUILD.gn b/content/BUILD.gn
index a8ef40a..2092909 100644
--- a/content/BUILD.gn
+++ b/content/BUILD.gn
@@ -9,7 +9,10 @@
 # Applied by targets internal to content.
 config("content_implementation") {
   defines = [ "CONTENT_IMPLEMENTATION" ]
-  configs = [ "//build/config/compiler:wexit_time_destructors" ]
+  configs = [
+    "//build/config/compiler:wexit_time_destructors",
+    "//build/config/compiler:noshadowing",
+  ]
 }
 
 # When targets depend on, e.g. //content/public/browser, what happens? To