Expose glResizeCHROMIUM() and remove some uses of MojoGLES2GetGLES2Interface().

examples/spinning_cube/gles2_client_impl.cc

Index: examples/spinning_cube/gles2_client_impl.cc
diff --git a/examples/spinning_cube/gles2_client_impl.cc b/examples/spinning_cube/gles2_client_impl.cc
index ce638ead891c0aca1c1c00a02186616feb9701e7..d74b0ba126dc14b4970be130cc19cceccd6cecdf 100644
--- a/examples/spinning_cube/gles2_client_impl.cc
+++ b/examples/spinning_cube/gles2_client_impl.cc
@@ -2,14 +2,18 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#ifndef GL_GLEXT_PROTOTYPES
+#define GL_GLEXT_PROTOTYPES
+#endif
+
 #include "examples/spinning_cube/gles2_client_impl.h"
 
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
+#include <GLES2/gl2extchromium.h>
 #include <math.h>
 #include <stdlib.h>
 
-#include "gpu/command_buffer/client/gles2_interface.h"
 #include "mojo/public/c/gles2/gles2.h"
 #include "mojo/public/cpp/environment/environment.h"
 #include "mojo/public/cpp/utility/run_loop.h"
@@ -48,10 +52,7 @@ void GLES2ClientImpl::SetSize(const mojo::Size& size) {
   cube_.set_size(size_.width, size_.height);
   if (size_.width == 0 || size_.height == 0 || !context_)
     return;
-  static_cast<gpu::gles2::GLES2Interface*>(
-      MojoGLES2GetGLES2Interface(context_))->ResizeCHROMIUM(size_.width,
-                                                            size_.height,
-                                                            1);
+  glResizeCHROMIUM(size_.width, size_.height, 1);

[jamesr, 2015/07/27 23:16:44]

i think the last parameter is a float, so you should write 1.f (i.e. the old
code was busted)

the reason for the glResizeCHROMIUM extension existing was to support handling
deviceScaleFactor changes in a natural way (i.e. scale content), but in Mojo the
graphics system is all in physical pixels (no implicit scaling) and surfaces are
not resizeable so this isn't really needed. we should probably instead provide
an explicit resize entry point to specify the onscreen context's width/height. 
This has to be in order with GL commands.  The easiest way to ensure ordering is
to put it in the command stream itself (like this) but we could also make it a
mojom entry point and require that the user flush before the call.

[viettrungluu, 2015/07/28 16:49:42]

Done (good to be explicit I guess, even if int -> float conversions are
automatic).

   WantToDraw();
 }