GLES1: Enable/disable for texture targets

BUG=angleproject:2306

Change-Id: I08ac9ef91753112f8185d16423925cf265f0384e
Reviewed-on: https://chromium-review.googlesource.com/1023987
Commit-Queue: Lingfeng Yang <lfy@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index 2a24712..22314ac 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -3011,6 +3011,7 @@
     {
         // Default extensions for GLES1
         supportedExtensions.pointSizeArray = true;
+        supportedExtensions.textureCubeMap = true;
     }
 
     if (getClientVersion() < ES_3_0)