Use black for blackout layer

SurfaceFlinger was rendering dark purple for secure content, which
showed up when we took a screen shot for the orientation change
animation.  Use black instead.

Bug 11157921

Change-Id: I3895e8168891d49dc5b84eed599bcd0a303bb70a
diff --git a/services/surfaceflinger/RenderEngine/GLES20RenderEngine.cpp b/services/surfaceflinger/RenderEngine/GLES20RenderEngine.cpp
index 7112ca8..a2a6270 100644
--- a/services/surfaceflinger/RenderEngine/GLES20RenderEngine.cpp
+++ b/services/surfaceflinger/RenderEngine/GLES20RenderEngine.cpp
@@ -50,7 +50,7 @@
         }
     } pack565;
 
-    const uint16_t protTexData[] = { pack565(0x03, 0x03, 0x03) };
+    const uint16_t protTexData[] = { 0 };
     glGenTextures(1, &mProtectedTexName);
     glBindTexture(GL_TEXTURE_2D, mProtectedTexName);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);