Correctly call glviewport when surface changes.

Change-Id: I7ef1539e39ea67245bac5ee410deb5918fc5dfcf
diff --git a/rsContext.cpp b/rsContext.cpp
index 8798612..1932108 100644
--- a/rsContext.cpp
+++ b/rsContext.cpp
@@ -446,6 +446,7 @@
 
     if (mWidth && mHeight) {
         mStateVertex.updateSize(this);
+        mFBOCache.updateSize();
     }
 }
 
diff --git a/rsFBOCache.h b/rsFBOCache.h
index f42e1f3..5d58ba4 100644
--- a/rsFBOCache.h
+++ b/rsFBOCache.h
@@ -38,6 +38,7 @@
     void resetAll(Context *);
 
     void setup(Context *);
+    void updateSize() { mDirty = true; }
 
     struct Hal {
         mutable void *drv;