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..cb7e569cc2b57968431a070c552d19a92ced8d58 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"
@@ -404,6 +427,16 @@ 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"

[michaelbai, 2016/09/19 19:06:13]

Sorry, I missed context here, could you show me where shlib_extension.whitelist
is defined and how lib_foo.$shlib_extension.whitelist is generated? I searched
code and can't figure it out.

[agrieve, 2016/09/19 19:10:32]

Searching for "enable_resource_whitelist_generation" is the key here.
This causes whitelists to be created as a part of compilation:
https://cs.chromium.org/chromium/src/build/toolchain/gcc_toolchain.gni?q=enab...

It doesn't solve the problem of excessive pragma warnings, but does at least
scope usages to specific .o files. Then, when linking the .o.whitelist files are
concatenated together.

This final generate_resource_whitelist() step actually just adds in 2 hard-coded
resource IDs on top of the .so.whitelist one.

[michaelbai, 2016/09/19 21:02:06]

Thanks for your explanation, now I understand how it works, but still have one
question, is shlib_extension.whitelist defined anywhere?

[agrieve, 2016/09/20 00:48:34]

shlib_extension is defined here: build/toolchain/toolchain.gni
.whitelist isn't a part of the expression (it's the file extension)

+    output = system_webview_pak_whitelist
+  }
+}
+
 source_set("common") {
   sources = [
     "browser/aw_browser_context.cc",