Enable global share context lock for chrome

Chrome only uses share contexts in GPU main thread, however chrome
use EGLImage to share texture cross share group between threads.
ANGLE will hold the global lock for EGL Image related APIs,
however some gl calls will need to access EGLImage as well. for
example: glDeleteTextures() glDeleteFramebuffers() will release
resources which are associated with EGLImage.

Bug: chromium:1444690,chromium:1444167,chromium:1394379
Change-Id: Icff5d13fb94f3576b59085ead90f72de4a2482a7
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4542990
Commit-Queue: Peng Huang <penghuang@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index cbc6c22..5da54a2 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -65,10 +65,7 @@
   angle_glesv2_extension = ""
 
   # Enable share context lock. If it is false, the client need to use gl calls in a threadsafe way.
-  # Chromium only uses share contexts on the GPU thread.
-  # angle_deqp_tests contains threading related tests.
-  angle_enable_share_context_lock =
-      !build_with_chromium || build_angle_deqp_tests
+  angle_enable_share_context_lock = true
 
   if (is_android) {
     # Use Android TLS slot to store current context.