Refactor GLSL array length method parsing

This prepares for accepting arbitrary expressions as the "this" node
of the array length method.

BUG=angleproject:2142
TEST=angle_unittests

Change-Id: I728adb6e76d2779dedbabfaeec7d096872e0d00d
Reviewed-on: https://chromium-review.googlesource.com/633945
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
diff --git a/src/compiler/translator/OutputTree.cpp b/src/compiler/translator/OutputTree.cpp
index f87a063..25e8298 100644
--- a/src/compiler/translator/OutputTree.cpp
+++ b/src/compiler/translator/OutputTree.cpp
@@ -318,6 +318,10 @@
             mOut << "Pre-Decrement";
             break;
 
+        case EOpArrayLength:
+            mOut << "Array length";
+            break;
+
         case EOpLogicalNotComponentWise:
             mOut << "component-wise not";
             break;