zero-copy: Clarify to allocate/destroy GpuMemoryBuffer on any thread and use it on the main thread o

ui/gl/gl_image_egl.cc

Index: ui/gl/gl_image_egl.cc
diff --git a/ui/gl/gl_image_egl.cc b/ui/gl/gl_image_egl.cc
index b8ee78c3a371575a33b9bbb8fa4d02678bf01333..ecec41fcdeef54fdb8bd4b24acff56e8365cd2d0 100644
--- a/ui/gl/gl_image_egl.cc
+++ b/ui/gl/gl_image_egl.cc
@@ -13,12 +13,14 @@ GLImageEGL::GLImageEGL(const gfx::Size& size)
 }
 
 GLImageEGL::~GLImageEGL() {
+  DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_EQ(EGL_NO_IMAGE_KHR, egl_image_);
 }
 
 bool GLImageEGL::Initialize(EGLenum target,
                             EGLClientBuffer buffer,
                             const EGLint* attrs) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_EQ(EGL_NO_IMAGE_KHR, egl_image_);
   egl_image_ = eglCreateImageKHR(GLSurfaceEGL::GetHardwareDisplay(),
                                  EGL_NO_CONTEXT,
@@ -35,6 +37,7 @@ bool GLImageEGL::Initialize(EGLenum target,
 }
 
 void GLImageEGL::Destroy(bool have_context) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   if (egl_image_ != EGL_NO_IMAGE_KHR) {
     eglDestroyImageKHR(GLSurfaceEGL::GetHardwareDisplay(), egl_image_);
     egl_image_ = EGL_NO_IMAGE_KHR;
@@ -44,6 +47,7 @@ void GLImageEGL::Destroy(bool have_context) {
 gfx::Size GLImageEGL::GetSize() { return size_; }
 
 bool GLImageEGL::BindTexImage(unsigned target) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_NE(EGL_NO_IMAGE_KHR, egl_image_);
   glEGLImageTargetTexture2DOES(target, egl_image_);
   DCHECK_EQ(static_cast<GLenum>(GL_NO_ERROR), glGetError());