Revert of Un-nest configs in GN files. (patchset #3 id:40001 of https://codereview.chromium.org/1318823008/ )

Reason for revert:
This breaks why these configs exist in the first place and seriously breaks the clang/win gn build (which is what these configs exist for).

Original issue's description:
> Un-nest configs in GN files.
>
> People sometimes nest targets or configs, usually with the assumption that this limits the visibility of a config to within a target. But this nesting provides no visibility restrictions over declaring it outside of a block.
>
> Un-nest for clarity.
>
> Committed: https://crrev.com/4af2eac8e84692d94f88504ab6e0b244b88dddcb
> Cr-Commit-Position: refs/heads/master@{#346461}

TBR=dpranke@chromium.org,brettw@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1316843006

Cr-Commit-Position: refs/heads/master@{#346695}

1 files changed, 8 insertions, 9 deletions

diff --git a/third_party/libpng/BUILD.gn b/third_party/libpng/BUILD.gn
index 2142059..c4e2650c 100644
--- a/third_party/libpng/BUILD.gn
+++ b/third_party/libpng/BUILD.gn
@@ -25,15 +25,6 @@ config("libpng_config") {
   }
 }
 
-# Must be in a config because of how GN orders flags (otherwise -Wall will
-# appear after this, and turn it back on).
-config("clang_warnings") {
-  if (is_clang) {
-    # Upstream uses self-assignment to avoid warnings.
-    cflags = [ "-Wno-self-assign" ]
-  }
-}
-
 source_set("libpng_sources") {
   sources = [
     "png.c",
@@ -71,6 +62,14 @@ source_set("libpng_sources") {
     "//third_party/zlib",
   ]
 
+  # Must be in a config because of how GN orders flags (otherwise -Wall will
+  # appear after this, and turn it back on).
+  config("clang_warnings") {
+    if (is_clang) {
+      # Upstream uses self-assignment to avoid warnings.
+      cflags = [ "-Wno-self-assign" ]
+    }
+  }
   configs += [ ":clang_warnings" ]
 }