create simple skia app for android using jni

platform_tools/android/examples/hello_skia_app/build.xml

Index: platform_tools/android/examples/hello_skia_app/build.xml
diff --git a/platform_tools/android/app/build.xml b/platform_tools/android/examples/hello_skia_app/build.xml
similarity index 64%
copy from platform_tools/android/app/build.xml
copy to platform_tools/android/examples/hello_skia_app/build.xml
index fbba716abbeae163260919bd3ea21f4ac74b732f..785b87b0a2e741110fe34e09b81f0e5aa015b158 100644
--- a/platform_tools/android/app/build.xml
+++ b/platform_tools/android/examples/hello_skia_app/build.xml
@@ -1,11 +1,42 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project name="SkiaAndroid" default="help">
+<project name="HelloSkia" default="help">
 
     <!-- The local.properties file is created and updated by the 'android' tool.
          It contains the path to the SDK. It should *NOT* be checked into
          Version Control Systems. -->
     <property file="local.properties" />
 
+    <!-- The ant.properties file can be created by you. It is only edited by the
+         'android' tool to add properties to it.
+         This is the place to change some Ant specific build properties.
+         Here are some properties you may want to change/update:
+
+         source.dir
+             The name of the source directory. Default is 'src'.
+         out.dir
+             The name of the output directory. Default is 'bin'.
+
+         For other overridable properties, look at the beginning of the rules
+         files in the SDK, at tools/ant/build.xml
+
+         Properties related to the SDK location or the project target should
+         be updated using the 'android' tool with the 'update' action.
+
+         This file is an integral part of the build system for your
+         application and should be checked into Version Control Systems.
+
+         -->
+    <property file="ant.properties" />
+
+    <!-- if sdk.dir was not set from one of the property file, then
+         get it from the ANDROID_HOME env var.
+         This must be done before we load project.properties since
+         the proguard config can use sdk.dir -->
+    <property environment="env" />
+    <condition property="sdk.dir" value="${env.ANDROID_HOME}">
+        <isset property="env.ANDROID_HOME" />
+    </condition>
+
     <!-- The project.properties file is created and updated by the 'android'
          tool, as well as ADT.
 
@@ -19,7 +50,7 @@
 
     <!-- quick check on sdk.dir -->
     <fail
-            message="sdk.dir is missing. Make sure to generate local.properties using 'android update project' or to inject it through an env var"
+            message="sdk.dir is missing. Make sure to generate local.properties using 'android update project' or to inject it through the ANDROID_HOME environment variable."
             unless="sdk.dir"
     />