Properly initialize FBO textures for linear filtering.

Change-Id: I67fc4fd760483ef85809be8d6e608cf4f469650f
diff --git a/libs/hwui/LayerRenderer.cpp b/libs/hwui/LayerRenderer.cpp
index 24f9739..b1eb164 100644
--- a/libs/hwui/LayerRenderer.cpp
+++ b/libs/hwui/LayerRenderer.cpp
@@ -214,6 +214,11 @@
     glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
             layer->texture, 0);
 
+    glDisable(GL_SCISSOR_TEST);
+    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    glEnable(GL_SCISSOR_TEST);
+
     glBindFramebuffer(GL_FRAMEBUFFER, previousFbo);
 
     return layer;