Implement GL_OES_EGL_image_external support.

BUG=14610416

Change-Id: I9ca6d1779c7b6f1b28d5d5665264815881ee01b5
Reviewed-on: https://swiftshader-review.googlesource.com/1071
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/GLES2/compiler/ParseHelper.cpp

diff --git a/src/GLES2/compiler/ParseHelper.cpp b/src/GLES2/compiler/ParseHelper.cpp
index af8fbbf..21a3fe7 100644
--- a/src/GLES2/compiler/ParseHelper.cpp
+++ b/src/GLES2/compiler/ParseHelper.cpp
@@ -326,16 +326,13 @@
         //
         // Type that can't be written to?
         //
-        switch (node->getBasicType()) {
-        case EbtSampler2D:
-        case EbtSamplerCube:
+        if(IsSampler(node->getBasicType()))
+        {
             message = "can't modify a sampler";
-            break;
-        case EbtVoid:
+        }
+        else if(node->getBasicType() == EbtVoid)
+        {
             message = "can't modify void";
-            break;
-        default: 
-            break;
         }
     }