Add support for ES3 MSAA.

include/gpu/gl/GrGLConfig.h

Index: include/gpu/gl/GrGLConfig.h
diff --git a/include/gpu/gl/GrGLConfig.h b/include/gpu/gl/GrGLConfig.h
index 1f7c9e29f5ec160ce67d16316a5f9d6e64c57bfd..0da2c0bf2c6fcb09d179311681127f3f06793c04 100644
--- a/include/gpu/gl/GrGLConfig.h
+++ b/include/gpu/gl/GrGLConfig.h
@@ -170,6 +170,15 @@
     #define GR_GL_USE_NEW_SHADER_SOURCE_SIGNATURE       0
 #endif
 
+// We now have a separate GrGLInterface function pointer entry for the IMG/EXT version of
+// glRenderbufferStorageMultisampled. However, Chrome is setting the one we now use for
+// ES3 MSAA to point to the IMG/EXT function. This macro exists to make Skia ignore the
+// ES3 MSAA and instead use the IMG/EXT version with the old function pointer entry. It will
+// be removed as soon as Chrome is updated to set the new function pointer.
+#if !defined(GR_GL_IGNORE_ES3_MSAA)
+    #define GR_GL_IGNORE_ES3_MSAA 0
+#endif
+
 /**
  * There is a strange bug that occurs on Macs with NVIDIA GPUs. We don't
  * fully understand it. When (element) array buffers are continually