windowManager: Replace custom shader with builtin ClutterEffects

While modal dialogs were attached to the parent's titlebar, it
made sense to leave the top of the parent window at full color.
With the new position of modal dialogs, it makes more sense to dim
the entire parent window, so we can use a combination of Clutter's
BrightnessContrast- and DesaturateEffect instead of our own custom
shader.

https://bugzilla.gnome.org/show_bug.cgi?id=674499

data/Makefile.am

@@ -73,17 +73,11 @@ all-local: gschemas.compiled
 convertdir = $(datadir)/GConf/gsettings
 convert_DATA = gnome-shell-overrides.convert
 
-shadersdir = $(pkgdatadir)/shaders
-shaders_DATA = \
-	shaders/dim-window.glsl
-
-
 EXTRA_DIST =						\
 	gnome-shell.desktop.in.in			\
 	gnome-shell-extension-prefs.desktop.in.in	\
 	$(introspection_DATA)				\
 	$(menu_DATA)					\
-	$(shaders_DATA)					\
 	$(convert_DATA)					\
 	org.gnome.shell.gschema.xml.in.in
 

data/shaders/dim-window.glsl

@@ -1,27 +0,0 @@
-#version 110
-uniform sampler2D tex;
-uniform float fraction;
-uniform float height;
-const float c = -0.2;
-const float border_max_height = 60.0;
-
-mat4 contrast = mat4 (1.0 + c, 0.0, 0.0, 0.0,
-                      0.0, 1.0 + c, 0.0, 0.0,
-                      0.0, 0.0, 1.0 + c, 0.0,
-                      0.0, 0.0, 0.0, 1.0);
-vec4 off = vec4(0.633, 0.633, 0.633, 0);
-void main()
-{
-  vec4 color = texture2D(tex, cogl_tex_coord_in[0].xy);
-  float y = height * cogl_tex_coord_in[0].y;
-
-  // To reduce contrast, blend with a mid gray
-  cogl_color_out = color * contrast - off * c * color.a;
-
-  // We only fully dim at a distance of BORDER_MAX_HEIGHT from the top and
-  // when the fraction is 1.0. For other locations and fractions we linearly
-  // interpolate back to the original undimmed color, so the top of the window
-  // is at full color.
-  cogl_color_out = color + (cogl_color_out - color) * max(min(y / border_max_height, 1.0), 0.0);
-  cogl_color_out = color + (cogl_color_out - color) * fraction;
-}