ES31: Remove support of GL_OES_geometry_shader in compiler

This patch intends to remove the support of GL_OES_geometry_shader
in ANGLE compiler.

To make the implementation simpler, currently we decide to only
support "GL_EXT_geometry_shader" as the extension string of geometry
shader in ANGLE.

This patch also updates all the related shaders in angle_unittests
into R"()" format.

BUG=angleproject:1941
TEST=angle_unittests

Change-Id: Ife9858abeedfb46b02c5c2fb1cda16fa27198511
Reviewed-on: https://chromium-review.googlesource.com/773451
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/compiler/translator/util.cpp b/src/compiler/translator/util.cpp
index 9738370..3ff4367 100644
--- a/src/compiler/translator/util.cpp
+++ b/src/compiler/translator/util.cpp
@@ -527,7 +527,7 @@
 bool IsGeometryShaderInput(GLenum shaderType, TQualifier qualifier)
 {
     return (qualifier == EvqGeometryIn) ||
-           ((shaderType == GL_GEOMETRY_SHADER_OES) && IsInterpolationIn(qualifier));
+           ((shaderType == GL_GEOMETRY_SHADER_EXT) && IsInterpolationIn(qualifier));
 }
 
 InterpolationType GetInterpolationType(TQualifier qualifier)