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

third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp

 // Copyright 2015 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 "modules/webgl/WebGL2RenderingContextBase.h"
 
 #include <memory>
 #include "bindings/modules/v8/WebGLAny.h"
 #include "core/frame/ImageBitmap.h"
 #include "core/html/HTMLCanvasElement.h"
@@ skipping 407 matching lines @@
                                                  GLint src_y1,
                                                  GLint dst_x0,
                                                  GLint dst_y0,
                                                  GLint dst_x1,
                                                  GLint dst_y1,
                                                  GLbitfield mask,
                                                  GLenum filter) {
   if (isContextLost())
     return;
 
+  DrawingBuffer::ScopedRGBEmulationForBlitFramebuffer emulation(
+      GetDrawingBuffer());
   ContextGL()->BlitFramebufferCHROMIUM(src_x0, src_y0, src_x1, src_y1, dst_x0,
                                        dst_y0, dst_x1, dst_y1, mask, filter);
 }
 
 bool WebGL2RenderingContextBase::ValidateTexFuncLayer(const char* function_name,
                                                       GLenum tex_target,
                                                       GLint layer) {
   if (layer < 0) {
     SynthesizeGLError(GL_INVALID_VALUE, function_name, "layer out of range");
     return false;
@@ skipping 5319 matching lines @@
 
 void WebGL2RenderingContextBase::
     DrawingBufferClientRestorePixelUnpackBufferBinding() {
   if (!ContextGL())
     return;
   ContextGL()->BindBuffer(GL_PIXEL_UNPACK_BUFFER,
                           ObjectOrZero(bound_pixel_unpack_buffer_.Get()));
 }
 
 }  // namespace blink