Fix using an alpha-less GL format for Android's RGBX.

Bug 19979126

Change-Id: Ic074079cbe3630751a95ffcc2b2b33700063abcf
Reviewed-on: https://swiftshader-review.googlesource.com/2782
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Ping-Hao Wu <pinghao@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
diff --git a/src/OpenGL/libGLESv2/Image.cpp b/src/OpenGL/libGLESv2/Image.cpp
index cfca395..821c21c 100644
--- a/src/OpenGL/libGLESv2/Image.cpp
+++ b/src/OpenGL/libGLESv2/Image.cpp
@@ -515,7 +515,7 @@
 	{
 		GLsizei inputPitch = ComputePitch(width, format, type, unpackAlignment);
 		void *buffer = lock(0, 0, sw::LOCK_WRITEONLY);
-		
+
 		if(buffer)
 		{
 			switch(type)
@@ -669,8 +669,9 @@
 		switch(format)
 		{
 		case HAL_PIXEL_FORMAT_RGBA_8888:
-		case HAL_PIXEL_FORMAT_RGBX_8888:
 			return GL_RGBA;
+		case HAL_PIXEL_FORMAT_RGBX_8888:
+			return GL_RGB;
 		case HAL_PIXEL_FORMAT_RGB_888:
 			return GL_RGB;
 		case HAL_PIXEL_FORMAT_RGB_565: