Fix INVALID_OPERATION error with layers rendering.

This change is a workaround for a driver bug that causes an INVALID_OPERATION
to be thrown on every glCopyTexSubImage() call. This change also adds a new
test for gradients local matrices.

Change-Id: I41b7437481026702d0a3a9677f099b4557c0a84e
diff --git a/libs/hwui/LayerCache.cpp b/libs/hwui/LayerCache.cpp
index 2770868..8c70cf9 100644
--- a/libs/hwui/LayerCache.cpp
+++ b/libs/hwui/LayerCache.cpp
@@ -114,6 +114,8 @@
         glGenTextures(1, &layer->texture);
         glBindTexture(GL_TEXTURE_2D, layer->texture);
 
+        glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
+
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);