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/libANGLE/Compiler.cpp b/src/libANGLE/Compiler.cpp
index b524520..ebcf028 100644
--- a/src/libANGLE/Compiler.cpp
+++ b/src/libANGLE/Compiler.cpp
@@ -132,8 +132,7 @@
     }
 
     // Geometry Shader constants
-    // TODO(jiawei.shao@intel.com): use EXT_geometry_shader everywhere in compiler.
-    mResources.OES_geometry_shader = extensions.geometryShader;
+    mResources.EXT_geometry_shader              = extensions.geometryShader;
     mResources.MaxGeometryUniformComponents     = caps.maxGeometryUniformComponents;
     mResources.MaxGeometryUniformBlocks         = caps.maxGeometryUniformBlocks;
     mResources.MaxGeometryInputComponents       = caps.maxGeometryInputComponents;