gpu: Bind dummy GL API when no context is current

ui/gl/gl_context.h

Index: ui/gl/gl_context.h
diff --git a/ui/gl/gl_context.h b/ui/gl/gl_context.h
index f40b1bba78647ab9ef7090ffa420e4c5ba1b739c..63589c7cf3827edf3a3e4c4e32071d7162ec3e75 100644
--- a/ui/gl/gl_context.h
+++ b/ui/gl/gl_context.h
@@ -117,6 +117,18 @@ class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
  protected:
   virtual ~GLContext();
 
+  // Will release the current context when going out of scope, unless canceled.
+  class ScopedReleaseCurrent {
+   public:
+    ScopedReleaseCurrent();
+    ~ScopedReleaseCurrent();
+
+    void Cancel();
+
+   private:
+    bool canceled_;
+  };
+
   // Sets the GL api to the real hardware API (vs the VirtualAPI)
   static void SetRealGLApi();
   virtual void SetCurrent(GLSurface* surface);