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/ShaderLang.cpp b/src/compiler/translator/ShaderLang.cpp
index eeb13f2..4da9409 100644
--- a/src/compiler/translator/ShaderLang.cpp
+++ b/src/compiler/translator/ShaderLang.cpp
@@ -203,7 +203,7 @@
     resources->ARM_shader_framebuffer_fetch    = 0;
     resources->OVR_multiview                   = 0;
     resources->EXT_YUV_target                  = 0;
-    resources->OES_geometry_shader             = 0;
+    resources->EXT_geometry_shader             = 0;
 
     resources->NV_draw_buffers = 0;