GL: remove obsolete Firefox workaround.

Reverts commit 4ce2875262 from 2015. This
is now also worked around directly in Emscripten:
6dc4ac5f9e/src/library_gl.js (L7361)

doc/changelog.dox

@@ -165,6 +165,8 @@ See also:
     possible as well
 -   The @ref GL::BufferUsage parameter in @ref GL::Buffer::setData() is now
     optional, defaults to @ref GL::BufferUsage::StaticDraw
+-   Re-enabled @fn_gl{DrawRangeElements} for WebGL 2 (see
+    [mosra/magnum#97](https://github.com/mosra/magnum/issues/97))
 
 @subsubsection changelog-latest-changes-math Math library
 

src/Magnum/GL/Mesh.cpp

@@ -411,8 +411,7 @@ void Mesh::drawInternal(Int count, Int baseVertex, Int instanceCount, GLintptr i
 
         /* Indexed mesh */
         } else {
-            /** @todo re-enable for WebGL 2.0 when glDrawRangeElements() no longer crashes Firefox */
-            #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
+            #ifndef MAGNUM_TARGET_GLES2
             /* Indexed mesh with specified range */
             if(indexEnd) {
                 glDrawRangeElements(GLenum(_primitive), indexStart, indexEnd, count, GLenum(_indexType), reinterpret_cast<GLvoid*>(indexOffset));