Add resource whitelisting to android_webview pak files.

android_webview/BUILD.gn

Index: android_webview/BUILD.gn
diff --git a/android_webview/BUILD.gn b/android_webview/BUILD.gn
index 90949095041e38ff459b30d08fb080bca95e68b1..c2cbd8bbb238725f21e511c4e3f4a07815143491 100644
--- a/android_webview/BUILD.gn
+++ b/android_webview/BUILD.gn
@@ -6,6 +6,7 @@ import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 import("//build/config/locales.gni")
 import("//tools/grit/repack.gni")
+import("//tools/resources/generate_resource_whitelist.gni")
 import("system_webview_apk_tmpl.gni")
 import("webview_repack_locales.gni")
 
@@ -18,6 +19,11 @@ if (!defined(use_webview_internal_framework)) {
   use_webview_internal_framework = false
 }
 
+if (enable_resource_whitelist_generation) {
+  system_webview_pak_whitelist =
+      "$target_gen_dir/system_webview_pak_whitelist.txt"
+}
+
 system_webview_android_manifest =
     "$target_gen_dir/system_webview_apk/AndroidManifest.xml"
 
@@ -38,6 +44,13 @@ jinja_template("system_webview_manifest") {
 webview_repack_locales("repack_locales") {
   input_locales = locales
   output_locales = locales
+
+  if (enable_resource_whitelist_generation) {
+    repack_whitelist = system_webview_pak_whitelist
+    deps = [
+      ":system_webview_pak_whitelist",
+    ]
+  }
 }
 
 locale_pak_resources("locale_paks") {
@@ -115,6 +128,11 @@ repack("repack_pack") {
     "//third_party/WebKit/public:resources",
   ]
   output = "$target_gen_dir/resources.pak"
+
+  if (enable_resource_whitelist_generation) {
+    repack_whitelist = system_webview_pak_whitelist
+    deps += [ ":system_webview_pak_whitelist" ]
+  }
 }
 
 repack("repack_100_percent") {
@@ -129,6 +147,11 @@ repack("repack_100_percent") {
     "//ui/resources",
   ]
   output = "$target_gen_dir/chrome_100_percent.pak"
+
+  if (enable_resource_whitelist_generation) {
+    repack_whitelist = system_webview_pak_whitelist
+    deps += [ ":system_webview_pak_whitelist" ]
+  }
 }
 
 webview_license_path = "$target_gen_dir/webview_licenses.notice"
@@ -267,7 +290,8 @@ grit("generate_components_strings") {
 
   # components_strings contains strings from all components. WebView
   # will never display most of them, so we try to limit the included
-  # strings
+  # strings. This whitelist trims about 50% more than the compile-based
+  # whitelist generated by :system_webview_pak_whitelist.
   whitelist = rebase_path("ui/grit_components_whitelist.txt")
   inputs = [
     whitelist,
@@ -404,6 +428,16 @@ if (android_64bit_target_cpu) {
   }
 }
 
+if (enable_resource_whitelist_generation) {
+  generate_resource_whitelist("system_webview_pak_whitelist") {
+    deps = [
+      ":libwebviewchromium",
+    ]
+    input = "$root_out_dir/libwebviewchromium$shlib_extension.whitelist"
+    output = system_webview_pak_whitelist
+  }
+}
+
 source_set("common") {
   sources = [
     "browser/aw_browser_context.cc",