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 c0a404c98ae7d6cff096ddd93f99c6b48a23e045..df4ce31d5af0ec9c3ea10df1c9e85b24b543d4c2 100644
--- a/ui/gl/gl_image_egl.cc
+++ b/ui/gl/gl_image_egl.cc
@@ -14,12 +14,14 @@ 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) {
     EGLBoolean result =
         eglDestroyImageKHR(GLSurfaceEGL::GetHardwareDisplay(), egl_image_);
@@ -49,6 +52,7 @@ 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());