Revert "Optimized discarding in fragment shaders on ES3"

This reverts commit dcb52b40df.

drape_frontend/shaders/colored_symbol.fsh.glsl

@@ -25,6 +25,8 @@ void main()
 
   lowp vec4 finalColor = color;
   finalColor.a = finalColor.a * u_opacity * (1.0 - alpha);
-  discardFragmentIfDepthEnabled(finalColor.a == 0.0);
+  if (finalColor.a == 0.0)
+    discard;
+
   gl_FragColor = finalColor;
 }

drape_frontend/shaders/discarded_texturing.fsh.glsl

@@ -11,6 +11,7 @@ void main()
 {
   vec4 finalColor = texture2D(u_colorTex, v_colorTexCoords);
   finalColor.a *= u_opacity;
-  discardFragmentIfDepthEnabled(finalColor.a < 0.01);
+  if (finalColor.a < 0.01)
+    discard;
   gl_FragColor = finalColor;
 }

drape_frontend/shaders/shaders_lib.glsl

@@ -46,18 +46,3 @@ vec4 samsungGoogleNexusWorkaround(vec4 color)
   return color;
 #endif
 }
-
-// This function discards fragment in ES2 mode or writes maximum value to the depth buffer
-// in ES3. It helps to avoid 'discard' invocation in cases when usual depth buffer mode is in use.
-void discardFragmentIfDepthEnabled(bool needDiscard)
-{
-#ifdef GLES3
-  if (needDiscard)
-    gl_FragDepth = 1.0;
-  else
-    gl_FragDepth = gl_FragCoord.z;
-#else
-  if (needDiscard)
-    discard;
-#endif
-}

drape_frontend/shaders/smaa_edges.fsh.glsl

@@ -39,7 +39,7 @@ void main()
   delta.xy = abs(L - vec2(Lleft, Ltop));
   vec2 edges = step(kThreshold, delta.xy);
   if (dot(edges, vec2(1.0, 1.0)) == 0.0)
-    discard;
+      discard;
 
   // Calculate right and bottom deltas.
   float Lright = dot(texture2D(u_colorTex, v_offset1.xy).rgb, kWeights);