Enable Skia to use GL fences with ES2 over ES3

This CL enables GL_APPLE_sync for Skia when we force it using ES2.0
on ES3.0 context.

Bug: 987286
Change-Id: If66d625a548ea486dbb4f376d91a55990d6760e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1774931Reviewed-by: Jonathan Backer <backer@chromium.org>
Commit-Queue: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691748}

ui/gl/init/create_gr_gl_interface.cc

@@ -679,6 +679,11 @@ sk_sp<GrGLInterface> CreateGrGLInterface(
       functions->fWaitSync = glWaitSyncEmulateEGL;
       functions->fDeleteSync = glDeleteSyncEmulateEGL;
     }
+  } else if (use_version_es2) {
+    // We have gl sync, but want to Skia use ES2 that doesn't have fences.
+    // To provide Skia with ways of sync to prevent it calling glFinish we set
+    // GL_APPLE_sync support.
+    extensions.add("GL_APPLE_sync");
   }
 
   functions->fGetInternalformativ = gl->glGetInternalformativFn;