Fix blits from multisampled renderbuffers to alpha:false WebGL back buffer.

ui/gl/gl_image_io_surface.mm

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gl/gl_image_io_surface.h"
 
 #include <map>
 
 #include "base/callback_helpers.h"
 #include "base/mac/bind_objc_block.h"
@@ skipping 150 matching lines @@
     case gfx::BufferFormat::YUV_420_BIPLANAR:
       NOTREACHED();
       return 0;
   }
 
   NOTREACHED();
   return 0;
 }
 
 // When an IOSurface is bound to a texture with internalformat "GL_RGB", many
-// OpenGL operations are broken. Therefore, never allow an IOSurface to be bound
-// with GL_RGB. https://crbug.com/595948.
+// OpenGL operations are broken. Therefore, don't allow an IOSurface to be bound
+// with GL_RGB unless overridden via BindTexImageWithInternalformat.
+// crbug.com/595948, crbug.com/699566.
 GLenum ConvertRequestedInternalFormat(GLenum internalformat) {
   if (internalformat == GL_RGB)
     return GL_RGBA;
   return internalformat;
 }
 
 }  // namespace
 
 GLImageIOSurface::GLImageIOSurface(const gfx::Size& size,
                                    unsigned internalformat)
@@ skipping 47 matching lines @@
 
 gfx::Size GLImageIOSurface::GetSize() {
   return size_;
 }
 
 unsigned GLImageIOSurface::GetInternalFormat() {
   return internalformat_;
 }
 
 bool GLImageIOSurface::BindTexImage(unsigned target) {
+  return BindTexImageWithInternalformat(target, 0);
+}
+
+bool GLImageIOSurface::BindTexImageWithInternalformat(unsigned target,
+                                                      unsigned internalformat) {
   DCHECK(thread_checker_.CalledOnValidThread());
   TRACE_EVENT0("gpu", "GLImageIOSurface::BindTexImage");
   base::TimeTicks start_time = base::TimeTicks::Now();
 
   // YUV_420_BIPLANAR is not supported by BindTexImage.
   // CopyTexImage is supported by this format as that performs conversion to RGB
   // as part of the copy operation.
   if (format_ == gfx::BufferFormat::YUV_420_BIPLANAR)
     return false;
 
   if (target != GL_TEXTURE_RECTANGLE_ARB) {
     // This might be supported in the future. For now, perform strict
     // validation so we know what's going on.
     LOG(ERROR) << "IOSurface requires TEXTURE_RECTANGLE_ARB target";
     return false;
   }
 
   CGLContextObj cgl_context =
       static_cast<CGLContextObj>(GLContext::GetCurrent()->GetHandle());
 
   DCHECK(io_surface_);
-  CGLError cgl_error =
-      CGLTexImageIOSurface2D(cgl_context, target, TextureFormat(format_),
-                             size_.width(), size_.height(), DataFormat(format_),
-                             DataType(format_), io_surface_.get(), 0);
+
+  GLenum texture_format =
+      internalformat ? internalformat : TextureFormat(format_);
+  CGLError cgl_error = CGLTexImageIOSurface2D(
+      cgl_context, target, texture_format, size_.width(), size_.height(),
+      DataFormat(format_), DataType(format_), io_surface_.get(), 0);
   if (cgl_error != kCGLNoError) {
     LOG(ERROR) << "Error in CGLTexImageIOSurface2D: "
                << CGLErrorString(cgl_error);
     return false;
   }
 
   UMA_HISTOGRAM_TIMES("GPU.IOSurface.TexImageTime",
                       base::TimeTicks::Now() - start_time);
   return true;
 }
@@ skipping 134 matching lines @@
 }
 
 // static
 GLImageIOSurface* GLImageIOSurface::FromGLImage(GLImage* image) {
   if (!image || image->GetType() != Type::IOSURFACE)
     return nullptr;
   return static_cast<GLImageIOSurface*>(image);
 }
 
 }  // namespace gl