Fix generate_split_manifest.py depending on third-party "lxml" import

build/android/gyp/generate_split_manifest.py

Index: build/android/gyp/generate_split_manifest.py
diff --git a/build/android/gyp/generate_split_manifest.py b/build/android/gyp/generate_split_manifest.py
index 93b55027dbba107dc390222cf039f52f77d68489..9cb3bca4b55f894fc1a9293eed7360b7500a0c6f 100755
--- a/build/android/gyp/generate_split_manifest.py
+++ b/build/android/gyp/generate_split_manifest.py
@@ -9,8 +9,8 @@ Given the manifest file for the main APK, generates an AndroidManifest.xml with
 the value required for a Split APK (package, versionCode, etc).
 """
 
-import lxml.etree
 import optparse
+import xml.etree.ElementTree
 
 from util import build_utils
 
@@ -66,8 +66,8 @@ def Build(main_manifest, split, has_code):
     The XML split manifest as a string
   """
 
-  doc = lxml.etree.fromstring(main_manifest)
-  package = doc.xpath('/manifest/@package')[0]
+  doc = xml.etree.ElementTree.fromstring(main_manifest)
+  package = doc.get('package')
 
   return MANIFEST_TEMPLATE % {
       'package': package,