Add android_library template

build/config/android/config.gni

Index: build/config/android/config.gni
diff --git a/build/config/android/config.gni b/build/config/android/config.gni
index 6a9080bcf86c93da40ff1b7c30f4370dd876412b..4cadc8b8b8707f50b7b1eec118d07bbbf00feba4 100644
--- a/build/config/android/config.gni
+++ b/build/config/android/config.gni
@@ -9,6 +9,9 @@ if (is_android) {
     # Absolute directory containing the Android source code.
     android_src = ""
 
+    android_sdk_root = "//third_party/android_tools/sdk"
+    android_sdk_version = "19"
+
     # This is set when building the Android WebView inside the Android build
     # system, using the 'android' gyp backend. The WebView code is still built
     # when this is unset, but builds using the normal chromium build system.
@@ -20,6 +23,9 @@ if (is_android) {
            "You must specify android_src for an Android WebView build.")
   }
 
+
+  android_sdk = "${android_sdk_root}/platforms/android-${android_sdk_version}"
+
   # android_ndk_root -----------------------------------------------------------
 
   # Full system path to the Android NDK.