fix some bit-rot in the ios port of sampleapp

BUG=skia:

Review URL: https://codereview.chromium.org/637263004
diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index ed57f11..2c17379 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -2381,6 +2381,7 @@
 }
 
 #ifdef SK_BUILD_FOR_IOS
+#include "SkApplication.h"
 IOS_launch_type set_cmd_line_args(int , char *[], const char* resourceDir) {
     SetResourcePath(resourceDir);
     return kApplication__iOSLaunchType;