Add GL_EXPORT for GLContextGLX

This fixes breakage of component_build on ChromeOS

BUG=129131
TEST=emerge and run chrome on ChromeOS

Review URL: https://chromiumcodereview.appspot.com/10399120

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@138430 0039d316-1c4b-4281-b951-d872f2087c98

ui/gl/gl_context_glx.h

@@ -11,13 +11,14 @@
 #include "base/compiler_specific.h"
 #include "ui/base/x/x11_util.h"
 #include "ui/gl/gl_context.h"
+#include "ui/gl/gl_export.h"
 
 namespace gfx {
 
 class GLSurface;
 
 // Encapsulates a GLX OpenGL context.
-class GLContextGLX : public GLContext {
+class GL_EXPORT GLContextGLX : public GLContext {
  public:
   explicit GLContextGLX(GLShareGroup* share_group);