Convert GN visibility variables to lists.

Currently this is either a list or a string. However, this is causing some problems because templates can't add to the invoker's visibility list without knowing if the original is a string or a list.

In an effort to make this consistent, I'm converting all visibiltiy to be lists, and will remove support for strings in a future build.

This exempts cld from header checking since it was confusing GN's header checker. It adds a ppapi header target as well that will be used by libyuv (that requires a roll).

TBR=scottmg

Review URL: https://codereview.chromium.org/544423002

Cr-Original-Commit-Position: refs/heads/master@{#293638}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 9af4262ad8020658ee04c07d13a2617af64147b1

secondary/testing/gtest/BUILD.gn

@@ -54,7 +54,7 @@ config("gtest_config") {
 }
 
 config("gtest_direct_config") {
-  visibility = ":*"
+  visibility = [ ":*" ]
   defines = [ "UNIT_TEST" ]
 }
 

secondary/third_party/cacheinvalidation/src/google/cacheinvalidation/BUILD.gn

@@ -6,7 +6,7 @@ import("//third_party/protobuf/proto_library.gni")
 
 proto_library("cacheinvalidation_proto_cpp") {
   # Depend on cacheinvalidation instead.
-  visibility = "//third_party/cacheinvalidation/*"
+  visibility = [ "//third_party/cacheinvalidation/*" ]
 
   sources = [
     "client.proto",

secondary/third_party/nss/BUILD.gn

@@ -385,7 +385,7 @@ if (is_linux) {
   # TODO(rsleevi): http://crbug.com/128134 - Break the circular dependency
   # without requiring nssckbi to be built as a shared library.
   source_set("nssckbi") {
-    visibility = ":nss"  # This target is internal implementation detail.
+    visibility = [ ":nss" ]  # This target is internal implementation detail.
 
     sources = [
       "nss/lib/ckfw/builtins/anchor.c",

secondary/tools/grit/grit_rule.gni

@@ -258,7 +258,7 @@ template("grit") {
   # The config and the action below get this visibility son only the generated
   # source set can depend on them. The variable "target_name" will get
   # overwritten inside the inner classes so we need to compute it here.
-  target_visibility = ":$target_name"
+  target_visibility = [ ":$target_name" ]
 
   # The current grit setup makes an file in $output_dir/grit/foo.h that
   # the source code expects to include via "grit/foo.h". It would be nice to
@@ -301,7 +301,16 @@ template("grit") {
 
     args += grit_flags + assert_files_flags
 
-    visibility = target_visibility
+    if (defined(invoker.visibility)) {
+      # This needs to include both what the invoker specified (since they
+      # probably include generated headers from this target), as well as the
+      # generated source set (since there's no guarantee that the visibility
+      # specified by the invoker includes our target).
+      #
+      # Only define visibility at all if the invoker specified it. Otherwise,
+      # we want to keep the public "no visibility specified" default.
+      visibility = target_visibility + invoker.visibility
+    }
 
     deps = [ "//tools/grit:grit_sources" ]
     if (defined(invoker.deps)) {

toolchain/win/midl.gni

@@ -37,7 +37,7 @@ template("midl") {
   type_library_file = "{{source_name_part}}.tlb"
 
   action_foreach(action_name) {
-    visibility = ":$source_set_name"
+    visibility = [ ":$source_set_name" ]
 
     # This functionality is handled by the win-tool because the GYP build has
     # MIDL support built-in.