Fix the source buffer used by CopyTex[Sub]Image.

We were passing the framebuffer to the texture's copying method, where
the first render target was used, instead of the read buffer.

Change-Id: I344b4082f675b7e5fc6a73af31a6764ab4d3b6a3
Reviewed-on: https://swiftshader-review.googlesource.com/17049
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
diff --git a/src/OpenGL/libGLESv2/libGLESv3.cpp b/src/OpenGL/libGLESv2/libGLESv3.cpp
index 12de6fb..0526254 100644
--- a/src/OpenGL/libGLESv2/libGLESv3.cpp
+++ b/src/OpenGL/libGLESv2/libGLESv3.cpp
@@ -749,7 +749,7 @@
 			return;
 		}
 
-		texture->copySubImage(target, level, xoffset, yoffset, zoffset, x, y, width, height, framebuffer);
+		texture->copySubImage(target, level, xoffset, yoffset, zoffset, x, y, width, height, source);
 	}
 }