Move the IndexRangeCache and Range types to the gl namespace.

BUG=angleproject:881

Change-Id: Ib05149facee9fcc7714cb957ca8647b3498a36b6
Reviewed-on: https://chromium-review.googlesource.com/269254
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index 545284a..4c26dbf 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -1224,7 +1224,7 @@
 
 Error Context::drawElements(GLenum mode, GLsizei count, GLenum type,
                             const GLvoid *indices, GLsizei instances,
-                            const rx::RangeUI &indexRange)
+                            const RangeUI &indexRange)
 {
     return mRenderer->drawElements(getData(), mode, count, type, indices, instances, indexRange);
 }