Ensure GL initialization only happens once, and provide common init path

ui/gl/gl_implementation_x11.cc

Index: ui/gl/gl_implementation_x11.cc
diff --git a/ui/gl/gl_implementation_x11.cc b/ui/gl/gl_implementation_x11.cc
index f85dff3609615f82c6120f75ec31c85d05fdd7ec..b78524990e8201aff5fc8036c27cec79e1d74000 100644
--- a/ui/gl/gl_implementation_x11.cc
+++ b/ui/gl/gl_implementation_x11.cc
@@ -43,8 +43,7 @@ bool InitializeStaticGLBindings(GLImplementation implementation) {
   // Prevent reinitialization with a different implementation. Once the gpu
   // unit tests have initialized with kGLImplementationMock, we don't want to
   // later switch to another GL implementation.
-  if (GetGLImplementation() != kGLImplementationNone)
-    return true;
+  DCHECK_EQ(kGLImplementationNone, GetGLImplementation());
 
   // Allow the main thread or another to initialize these bindings
   // after instituting restrictions on I/O. Going forward they will