Revert "Merge pull request #2330 from ShabbyX/optimize_for_angle"

This reverts commit 1ee5d1c0bb683daea245e8329fd619940a35a5b4, reversing
changes made to 906d48a7e828701e25487c9cf34418ded831c814.
diff --git a/BUILD.gn b/BUILD.gn
index dc3eb06..7242b6f 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -109,6 +109,7 @@
       "SPIRV/SpvBuilder.cpp",
       "SPIRV/SpvBuilder.h",
       "SPIRV/SpvPostProcess.cpp",
+      "SPIRV/SpvTools.cpp",
       "SPIRV/SpvTools.h",
       "SPIRV/bitutils.h",
       "SPIRV/disassemble.cpp",
@@ -155,7 +156,7 @@
       "glslang/MachineIndependent/attribute.cpp",
       "glslang/MachineIndependent/attribute.h",
       "glslang/MachineIndependent/gl_types.h",
-      "glslang/MachineIndependent/glslang_angle_tab.cpp.h",
+      "glslang/MachineIndependent/glslang_tab.cpp",
       "glslang/MachineIndependent/glslang_tab.cpp.h",
       "glslang/MachineIndependent/intermOut.cpp",
       "glslang/MachineIndependent/iomapper.cpp",
@@ -206,25 +207,9 @@
     }
 
     defines = []
-    if (invoker.is_angle) {
-      sources += [
-        "glslang/MachineIndependent/glslang_angle_tab.cpp",
-      ]
-      defines += [ "GLSLANG_ANGLE" ]
-    }
-    else {
-      sources += [
-        "glslang/MachineIndependent/glslang_tab.cpp",
-      ]
-    }
-
     if (invoker.enable_opt) {
-      sources += [ "SPIRV/SpvTools.cpp" ]
       defines += [ "ENABLE_OPT=1" ]
     }
-    if (invoker.is_angle) {
-      defines += [ "GLSLANG_ANGLE" ]
-    }
 
     if (is_win) {
       sources += [ "glslang/OSDependent/Windows/ossource.cpp" ]
@@ -272,13 +257,11 @@
 glslang_sources_common("glslang_lib_sources") {
   enable_opt = !glslang_angle
   enable_hlsl = !glslang_angle
-  is_angle = glslang_angle
 }
 
 glslang_sources_common("glslang_sources") {
   enable_opt = true
   enable_hlsl = true
-  is_angle = false
 }
 
 source_set("glslang_default_resource_limits_sources") {