Fix error checks on compute context creation.
Remove GL init for compute scripts.

Change-Id: I1bce8e4112babf4345fa56a30a9bed753734d8d6
diff --git a/graphics/java/android/renderscript/RenderScript.java b/graphics/java/android/renderscript/RenderScript.java
index 4c505ec..eea0986c 100644
--- a/graphics/java/android/renderscript/RenderScript.java
+++ b/graphics/java/android/renderscript/RenderScript.java
@@ -839,6 +839,9 @@
 
         rs.mDev = rs.nDeviceCreate();
         rs.mContext = rs.nContextCreate(rs.mDev, 0);
+        if (rs.mContext == 0) {
+            throw new RSDriverException("Failed to create RS context.");
+        }
         rs.mMessageThread = new MessageThread(rs);
         rs.mMessageThread.start();
         return rs;