[Xamarin.Android.Tools.AndroidSdk] Export JAVA_HOME, PATH on Windows (#30)

Context: https://paper.dropbox.com/doc/OpenJDK-and-You--AH1yWKdVXgno~uXYfmcUAZTwAg-NoECAe2XkBQeoxFfGL6ea

On Windows, set the `%JAVA_HOME%` and `%PATH%` environment variables
so that they contain the `AndroidSdkInfo.JavaSdkPath` value.
This ensures that related tools *launched from Visual Studio*, such
as the Android Device Manager, use the same
`AndroidSdkInfo.JavaSdkPath` value as the rest of the Xamarin.Android
tooling, and not whatever system-wide `%JAVA_HOME%` value may have
been previously set.

Author: tondat

src/Xamarin.Android.Tools.AndroidSdk/Sdks/AndroidSdkWindows.cs

@@ -222,5 +222,26 @@ private bool CheckRegistryKeyForExecutable (UIntPtr key, string subkey, string v
 			return true;
 		}
 		#endregion
+
+		public override void Initialize (string androidSdkPath = null, string androidNdkPath = null, string javaSdkPath = null)
+		{
+			base.Initialize (androidSdkPath, androidNdkPath, javaSdkPath);
+
+			var jdkPath = JavaSdkPath;
+			if (!string.IsNullOrEmpty (jdkPath)) {
+				var cur = Environment.GetEnvironmentVariable ("JAVA_HOME");
+				if (!string.IsNullOrEmpty (cur))
+					Environment.SetEnvironmentVariable ("JAVA_HOME", jdkPath);
+
+				var javaBinPath = this.JavaBinPath;
+				if (!string.IsNullOrEmpty (javaBinPath)) {
+					var environmentPath = Environment.GetEnvironmentVariable ("PATH");
+					if (!environmentPath.Contains (javaBinPath)) {
+						var processPath = string.Concat (javaBinPath, Path.PathSeparator, environmentPath);
+						Environment.SetEnvironmentVariable ("PATH", processPath);
+					}
+				}
+			}
+		}
 	}
 }