Merge to XFA: Add standard "Must be after no_chromium_code" comment in GN files.

R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1411563004 .

(cherry picked from commit 4793f674f29be8bf06a60672032e2e2df5164c8c)

Review URL: https://codereview.chromium.org/1415573006 .
diff --git a/BUILD.gn b/BUILD.gn
index 00b4775..52e701e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -581,8 +581,7 @@
   configs += [
     ":pdfium_config",
     "//build/config/compiler:no_chromium_code",
-    # As of this writing, this needs to be last to suppress a -Wswitch warning.
-    # https://crbug.com/547906
+    # Must be after no_chromium_code for warning flags to be ordered correctly.
     ":fxge_warnings",
   ]
 
diff --git a/third_party/BUILD.gn b/third_party/BUILD.gn
index 5814a7d..7c31e56 100644
--- a/third_party/BUILD.gn
+++ b/third_party/BUILD.gn
@@ -30,11 +30,22 @@
   ]
 }
 
+config("fx_freetype_warnings") {
+  visibility = [ ":*" ]
+  if (is_clang) {
+    # open_face_PS_from_sfnt_stream() and open_face_from_buffer() in
+    # ftbase.h are unused.
+    cflags = [ "-Wno-unused-function" ]
+  }
+}
+
 source_set("fx_freetype") {
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
     "//build/config/compiler:no_chromium_code",
     "//third_party/pdfium:pdfium_config",
+    # Must be after no_chromium_code for warning flags to be ordered correctly.
+    ":fx_freetype_warnings",
   ]
   defines = [ "FT2_BUILD_LIBRARY" ]
   sources = [
@@ -69,11 +80,21 @@
   ]
 }
 
+config("fx_agg_warnings") {
+  visibility = [ ":*" ]
+  if (is_clang) {
+    # calc_butt_cap() in agg_vcgen_stroke.cpp is unused.
+    cflags = [ "-Wno-unused-function" ]
+  }
+}
+
 source_set("fx_agg") {
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
     "//build/config/compiler:no_chromium_code",
     "//third_party/pdfium:pdfium_config",
+    # Must be after no_chromium_code for warning flags to be ordered correctly.
+    ":fx_agg_warnings",
   ]
   sources = [
     "agg23/agg_basics.h",
@@ -107,6 +128,7 @@
   configs += [
     "//build/config/compiler:no_chromium_code",
     "//third_party/pdfium:pdfium_config",
+    # Must be after no_chromium_code for warning flags to be ordered correctly.
     ":fx_lcms2_warnings",
   ]
   sources = [