Take GL version and extensions correctly into account when binding functions

ui/gl/gl_surface_wgl.cc

Index: ui/gl/gl_surface_wgl.cc
diff --git a/ui/gl/gl_surface_wgl.cc b/ui/gl/gl_surface_wgl.cc
index 7e1c3a7ad1fe9f2ec1cf127ba6eeadfb1f80b0b3..a865b42a7abcde10c44bd1fdd7999933f3a371ea 100644
--- a/ui/gl/gl_surface_wgl.cc
+++ b/ui/gl/gl_surface_wgl.cc
@@ -164,7 +164,10 @@ bool GLSurfaceWGL::InitializeOneOff() {
   if (!wgl_display->Init())
     return false;
 
-  // Create a temporary GL context to bind to extension entry points.
+  // Create a temporary GL context to bind to entry points. wglGetProcAddress
+  // is specified to return NULL for all queries if a context is not current in
+  // MSDN documentation, and the static bindings may contain functions that
+  // need to be queried with wglGetProcAddress.
   HGLRC gl_context = wglCreateContext(wgl_display->device_context());

[no sievers, 2013/12/05 20:51:57]

Should this move into gl_implementation_win.cc:InitializeStaticGLBindings()?

InitializeStaticGLBindings() seems flaky otherwise (well it was before your
patch, so feel free to put a TODO and DCHECK() for a current context).

[oetuaho, 2013/12/09 17:17:07]

Yeah, this needs a fix. GLSurface::InitializeOneOff calls first into
InitializeStaticGLBindings without a current context. It should be relatively
safe according to MSDN documentation, which says that wglGetProcAddress should
return NULL if there's no current context, so only OpenGL 1.1 entry points
exported by the dll should be set, and the remaining entry points would be set
here. But http://www.opengl.org/wiki/Load_OpenGL_Functions warns that actual
implementations sometimes return numbers from -1 to 3 on errors.

After finding out this, I think there's no real alternative to moving the code
over to gl_implementation_win.cc::InitializeStaticGLBindings, so I'll do that.

   if (!gl_context) {
     LOG(ERROR) << "Failed to create temporary context.";
@@ -175,10 +178,8 @@ bool GLSurfaceWGL::InitializeOneOff() {
     wglDeleteContext(gl_context);
     return false;
   }
-  // Get bindings to extension functions that cannot be acquired without a
-  // current context.
-  InitializeGLBindingsGL();
-  InitializeGLBindingsWGL();
+  InitializeStaticGLBindingsGL();
+  InitializeStaticGLBindingsWGL();
 
   wglMakeCurrent(NULL, NULL);
   wglDeleteContext(gl_context);