Add an extension to share textures at the display level.

BUG=angleproject:1639

Change-Id: If9140142ebce89f33921c13d9d212c17d1894162
Reviewed-on: https://chromium-review.googlesource.com/437618
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index 96c7c8a..6f04a4c 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -236,10 +236,12 @@
 Context::Context(rx::EGLImplFactory *implFactory,
                  const egl::Config *config,
                  const Context *shareContext,
+                 TextureManager *shareTextures,
                  const egl::AttributeMap &attribs,
                  const egl::DisplayExtensions &displayExtensions)
 
     : ValidationContext(shareContext,
+                        shareTextures,
                         GetClientVersion(attribs),
                         &mGLState,
                         mCaps,