Fix projection offset caching

Because the caching of projection matrix didn't account for changes in
the offset flag, the flag could be ignored. Now we use both to verify
that the cached matrix can be used.

Change-Id: I193b94eaf0b98f046a6484f0866c3d25048653fd
diff --git a/libs/hwui/Program.h b/libs/hwui/Program.h
index bc0f211..5dfb2fa 100644
--- a/libs/hwui/Program.h
+++ b/libs/hwui/Program.h
@@ -431,6 +431,7 @@
     bool mHasSampler;
 
     mat4 mProjection;
+    bool mOffset;
 }; // class Program
 
 }; // namespace uirenderer