Do not convert 8888 bitmaps to 565 when doing a copy.

Bug #2988077
This change keeps the 8888 format for new bitmaps and also keeps,
when possible, the opaque flag.

Change-Id: Ia61f2e89936916b329212a4c59a7d815c329f84e
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index 47ab355..f70bca7 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -133,6 +133,7 @@
 
     glViewport(0, 0, mWidth, mHeight);
 
+    glDisable(GL_DITHER);
     glDisable(GL_SCISSOR_TEST);
 
     glClearColor(0.0f, 0.0f, 0.0f, 0.0f);