[Android] Add support for standalone PDFium gn build on Android.
This pulls in the android NDK and catapult, rolls chromium/src/build/,
and pulls in two .gni updates. It also fixes a few miscellaneous compile
failures in android-specific code.
BUG=pdfium:38
Review-Url: https://codereview.chromium.org/2059553002
diff --git a/.gitignore b/.gitignore
index c8dc4a0..7b6ce1d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,8 @@
/testing/corpus
/testing/gmock
/testing/gtest
+/third_party/android_ndk
+/third_party/catapult
/third_party/icu
/third_party/llvm
/third_party/llvm-build
