create simple skia app for android using jni

platform_tools/android/examples/hello_skia_app/build.xml

 <?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.
 
          This contains project specific properties such as project target, and library
          dependencies. Lower level build properties are stored in ant.properties
          (or in .classpath for Eclipse projects).
 
          This file is an integral part of the build system for your
          application and should be checked into Version Control Systems. -->
     <loadproperties srcFile="project.properties" />
 
     <!-- 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"
     />
 
     <!--
         Import per project custom build rules if present at the root of the project.
         This is the place to put custom intermediary targets such as:
             -pre-build
             -pre-compile
             -post-compile (This is typically used for code obfuscation.
                            Compiled code location: ${out.classes.absolute.dir}
@@ skipping 19 matching lines @@
          ***********************
          ****** IMPORTANT ******
          ***********************
          In all cases you must update the value of version-tag below to read 'custom' instead of an integer,
          in order to avoid having your file be overridden by tools such as "android update project"
     -->
     <!-- version-tag: 1 -->
     <import file="${sdk.dir}/tools/ant/build.xml" />
 
 </project>