Revert "Implement gl_FragDepth for GLES SL 3.0"

assertion failures in WebGL2 CTS.

This reverts commit 544809610a131fe7040f2212789c62e212bbaf24.

Change-Id: I2e0c7045c5b6ef9031a6e6c5916504fe68f51077
Reviewed-on: https://chromium-review.googlesource.com/287910
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/compiler/translator/Initialize.cpp b/src/compiler/translator/Initialize.cpp
index ef7a2d9..6cb2e22 100644
--- a/src/compiler/translator/Initialize.cpp
+++ b/src/compiler/translator/Initialize.cpp
@@ -504,18 +504,10 @@
 
             if (resources.EXT_frag_depth)
             {
-                symbolTable.insert(
-                    ESSL1_BUILTINS, "GL_EXT_frag_depth",
-                    new TVariable(
-                        NewPoolTString("gl_FragDepthEXT"),
-                        TType(EbtFloat, resources.FragmentPrecisionHigh ? EbpHigh : EbpMedium,
-                              EvqFragDepthEXT, 1)));
+                symbolTable.insert(ESSL1_BUILTINS, "GL_EXT_frag_depth", new TVariable(NewPoolTString("gl_FragDepthEXT"),
+                    TType(EbtFloat, resources.FragmentPrecisionHigh ? EbpHigh : EbpMedium, EvqFragDepth, 1)));
             }
 
-            symbolTable.insert(ESSL3_BUILTINS,
-                               new TVariable(NewPoolTString("gl_FragDepth"),
-                                             TType(EbtFloat, EbpHigh, EvqFragDepth, 1)));
-
             if (resources.EXT_shader_framebuffer_fetch || resources.NV_shader_framebuffer_fetch)
             {
                 TType lastFragData(EbtFloat, EbpMedium, EvqLastFragData, 4, 1, true);