Update Android Apps to use gradle

This CL replaces ant with gradle for the task of building APKs.
The primary driver of this change is that it now allow us to
develop and test our apps using Android Studio.
DOCS_PREVIEW= https://skia.org/?cl=1215023017

Committed: https://skia.googlesource.com/skia/+/425535f1626932e4e22f61a2571f9c3c2b1c5977

Review URL: https://codereview.chromium.org/1215023017
diff --git a/.gitignore b/.gitignore
index 44d423f..7ea8256 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,9 +1,12 @@
 *.pyc
 *.swp
+*.iml
 .DS_Store
 .android_config
 .gclient*
 .gm-actuals
+.gradle
+.idea
 .cproject
 .project
 .settings/
@@ -12,6 +15,10 @@
 common
 gyp/build
 out
+platform_tools/android/apps/build
+platform_tools/android/apps/*.properties
+platform_tools/android/apps/*/build
+platform_tools/android/apps/*/src/main/libs
 platform_tools/chromeos/third_party/externals
 platform_tools/chromeos/toolchain
 skps