Add support for ES3 MSAA.

include/gpu/gl/GrGLInterface.h

Index: include/gpu/gl/GrGLInterface.h
===================================================================
--- include/gpu/gl/GrGLInterface.h	(revision 10891)
+++ include/gpu/gl/GrGLInterface.h	(working copy)
@@ -223,7 +223,29 @@
     GLPtr<GrGLReadBufferProc> fReadBuffer;
     GLPtr<GrGLReadPixelsProc> fReadPixels;
     GLPtr<GrGLRenderbufferStorageProc> fRenderbufferStorage;
+
+#if !GR_GL_IGNORE_ES3_MSAA
+    //  On OpenGL ES there are multiple incompatible extensions that add support for MSAA
+    //  and ES3 adds MSAA support to the standard. On an ES3 driver we may still use the
+    //  older extensions for performance reasons or due to ES3 driver bugs. We want the function
+    //  that creates the GrGLInterface to provide all available functions and internally
+    //  we will select among them. They all have a method called glRenderbufferStorageMultisample*.
+    //  So we have separate function pointers for GL_IMG/EXT_multisampled_to_texture,
+    //  GL_CHROMIUM/ANGLE_framebuffer_multisample/ES3, and GL_APPLE_framebuffer_multisample
+    //  variations.
+    //
+    //  If a driver supports multiple GL_ARB_framebuffer_multisample-style extensions then we will
+    //  assume the function pointers for the standard (or equivalent GL_ARB) version have
+    //  been preferred over GL_EXT, GL_CHROMIUM, or GL_ANGLE variations that have reduced
+    //  functionality.
+
+    //  GL_EXT_multisampled_render_to_texture (preferred) or GL_IMG_multisampled_render_to_texture
+    GLPtr<GrGLRenderbufferStorageMultisampleProc> fRenderbufferStorageMultisampleES2EXT;
+    //  GL_APPLE_framebuffer_multisample
+    GLPtr<GrGLRenderbufferStorageMultisampleProc> fRenderbufferStorageMultisampleES2APPLE;
+#endif

[jvanverth1, 2013/08/27 17:39:06]

Maybe a comment here stating that this is where
GL_CHROMIUM/ANGLE_framebuffer_multisample/ES3 is stored? Just to be consistent
with the other two comments.

[bsalomon, 2013/09/05 22:00:15]

Done.

     GLPtr<GrGLRenderbufferStorageMultisampleProc> fRenderbufferStorageMultisample;
+
     GLPtr<GrGLRenderbufferStorageMultisampleCoverageProc> fRenderbufferStorageMultisampleCoverage;
     GLPtr<GrGLResolveMultisampleFramebufferProc> fResolveMultisampleFramebuffer;
     GLPtr<GrGLScissorProc> fScissor;