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

ui/gl/gl_image_io_surface.mm

Index: ui/gl/gl_image_io_surface.mm
diff --git a/ui/gl/gl_image_io_surface.mm b/ui/gl/gl_image_io_surface.mm
index fc4df49f478ff007cbbfd681ce8c63cd8493582d..8e208301e57902cad93055c22c1eff6bcc0ef8f7 100644
--- a/ui/gl/gl_image_io_surface.mm
+++ b/ui/gl/gl_image_io_surface.mm
@@ -168,9 +168,8 @@ GLenum DataType(gfx::BufferFormat format) {
 }
 
 // When an IOSurface is bound to a texture with internalformat "GL_RGB", many
-// 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.
+// OpenGL operations are broken. Therefore, never allow an IOSurface to be bound
+// with GL_RGB. https://crbug.com/595948.
 GLenum ConvertRequestedInternalFormat(GLenum internalformat) {
   if (internalformat == GL_RGB)
     return GL_RGBA;
@@ -238,11 +237,6 @@ unsigned GLImageIOSurface::GetInternalFormat() {
 }
 
 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();
@@ -264,12 +258,10 @@ bool GLImageIOSurface::BindTexImageWithInternalformat(unsigned target,
       static_cast<CGLContextObj>(GLContext::GetCurrent()->GetHandle());
 
   DCHECK(io_surface_);
-
-  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);
+  CGLError cgl_error =
+      CGLTexImageIOSurface2D(cgl_context, target, TextureFormat(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);