Platform: properly escape output on windowless Emscripten app.

doc/changelog.dox

@@ -116,6 +116,7 @@ r<Player<T, K>>>)
 -   Don't assert in DPI scaling detection in @ref Platform::Sdl2Application and
     @ref Platform::GlfwApplication on X11 DEs that don't create any
     `RESOURCE_MANAGER` (see [mosra/magnum#290](https://github.com/mosra/magnum/issues/290))
+-   Properly escaping log output on Emscripten @ref Platform::WindowlessEglApplication
 -   The @ref GL::Context::States enum set was missing value combining operators
 -   Fixed @ref Text::DistanceFieldGlyphCache internal formats on ES2 devices
     that support @gl_extension{EXT,texture_storage} (see

src/Magnum/Platform/WindowlessEmscriptenApplication.js

@@ -33,12 +33,18 @@ var Module = {
 
     printErr: function(message) {
         var log = document.getElementById('log');
-        log.innerHTML += Array.prototype.slice.call(arguments).join(' ') + '\n';
+        log.innerHTML += Array.prototype.slice.call(arguments).join(' ')
+            .replace(/[\"&<>]/g, function (a) {
+                return { '"': '&quot;', '&': '&amp;', '<': '&lt;', '>': '&gt;' }[a];
+            }) + '\n';
     },
 
     print: function(message) {
         var log = document.getElementById('log');
-        log.innerHTML += Array.prototype.slice.call(arguments).join(' ') + '\n';
+        log.innerHTML += Array.prototype.slice.call(arguments).join(' ')
+            .replace(/[\"&<>]/g, function (a) {
+                return { '"': '&quot;', '&': '&amp;', '<': '&lt;', '>': '&gt;' }[a];
+            }) + '\n';
     },
 
     /* onAbort not handled here, as the output is printed directly on the page */