gpu: Cleanup class/struct forward declarations

gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.h

Index: gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.h
diff --git a/gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.h b/gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.h
index cc3c6319da8373bc28f3d6d216abd7282baa421c..497b8c68d386e5ed47125895afa0c242a736bd60 100644
--- a/gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.h
+++ b/gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.h
@@ -8,10 +8,6 @@
 #include "gpu/command_buffer/service/gl_utils.h"
 #include "gpu/gpu_export.h"
 
-namespace {
-class CMAAEffect;
-}
-
 namespace gpu {
 namespace gles2 {
 class CopyTextureCHROMIUMResourceManager;