[android_webview] Enable new android_webview resource target on Android.

android_webview/build/resources_config.mk

Index: android_webview/build/resources_config.mk
diff --git a/android_webview/build/resources_config.mk b/android_webview/build/resources_config.mk
index f9ab1352621b6cabd34354f141fa0fc9c3a202bc..f32ef6f61fd481e8621989ab770eb3a799179848 100644
--- a/android_webview/build/resources_config.mk
+++ b/android_webview/build/resources_config.mk
@@ -4,8 +4,15 @@
 
 android_webview_manifest_file := $(call my-dir)/AndroidManifest.xml
 
-# resources
+# Resources.
+# The res_hack folder is necessary to defeat a build system "optimization" which
+# ends up skipping running aapt if there are no resource files in any of the
+# resources dirs. Unfortunately, because all of our resources are generated at
+# build time and because this check is performed when processing the Makefile
+# it tests positive when building from clean resulting in a build failure.
+# We defeat the optimization by including an empty values.xml file in the list.
 android_webview_resources_dirs := \
+    $(call my-dir)/res_hack \
     $(call intermediates-dir-for,GYP,shared,,,$(TARGET_2ND_ARCH))/android_webview_jarjar_content_resources/jarjar_res \
     $(call intermediates-dir-for,GYP,shared,,,$(TARGET_2ND_ARCH))/android_webview_jarjar_ui_resources/jarjar_res \
     $(call intermediates-dir-for,GYP,ui_strings_grd,,,$(TARGET_2ND_ARCH))/ui_strings_grd/res_grit \