Add initial GpuMemoryBufferSurfaceTexture implementation.

ui/gl/gl_image_surface_texture.cc

+// Copyright 2014 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_surface_texture.h"
+
+#include "base/debug/trace_event.h"
+#include "ui/gl/android/surface_texture.h"
+#include "ui/gl/android/surface_texture_tracker.h"
+#include "ui/gl/gl_bindings.h"
+
+namespace gfx {
+namespace {
+
+// This is admittedly a bit ugly. SurfaceTexture API takes ownership of texture
+// ids when AttachToGLContext() is called and will delete the texture unless
+// DetachFromGLContext() is called with no context current. This helper class
+// can be used to temporarily make no context current for the purpose of
+// stealing the texture id of a given surface texture.
+class ScopedNoContextCurrent {
+ public:
+  ScopedNoContextCurrent()
+      : display_(eglGetCurrentDisplay()),
+        context_(eglGetCurrentContext()),
+        draw_surface_(eglGetCurrentSurface(EGL_DRAW)),
+        read_surface_(eglGetCurrentSurface(EGL_READ)) {
+    eglMakeCurrent(display_, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+  }
+
+  ~ScopedNoContextCurrent() {
+    eglMakeCurrent(display_, draw_surface_, read_surface_, context_);
+  }
+
+ private:
+  EGLDisplay display_;
+  EGLContext context_;
+  EGLSurface draw_surface_;
+  EGLSurface read_surface_;
+};
+
+void DetachFromGLContext(SurfaceTexture* surface_texture) {
+  // Detach with no context current to prevent SurfaceTexture from deleting
+  // currently attached texture id.
+  ScopedNoContextCurrent no_context_current;
+  surface_texture->DetachFromGLContext();
+}
+
+}  // namespace
+
+GLImageSurfaceTexture::GLImageSurfaceTexture(gfx::Size size)
+    : size_(size), texture_id_(0) {}
+
+GLImageSurfaceTexture::~GLImageSurfaceTexture() { Destroy(); }
+
+bool GLImageSurfaceTexture::Initialize(gfx::GpuMemoryBufferHandle buffer) {
+  DCHECK(!surface_texture_);
+  surface_texture_ =
+      SurfaceTextureTracker::GetInstance()->AcquireSurfaceTexture(

[no sievers, 2014/03/18 20:58:13]

This handle comes from the client, so we also need to avoid somehow that a
malicious renderer can get access to another renderer's texture and modify it.
(Even if cannot get the Surface handle, because there we do check the child
process id, it could still modify the texture through other means.)

You can get the renderer_pid() from GpuChannel.

Or we could also avoid the problem similar to how we do it on other platforms by
not having a global surface tracker, but instead not making lookup possible
outside of the context group here.

[reveman, 2014/03/24 18:35:07]

Gpu memory buffers are global on other platforms. Once you've created a gpu
memory buffer, you can register it with any command buffer instance you like.
Security comes from ownership being passed by the IPC system, which is of course
not the case with surface textures on Android.

Latest patch should address this. The gpu service is now validating the surface
texture id before registering the gpu memory buffer.

+          buffer.surface_texture_id);
+  return !!surface_texture_;
+}
+
+void GLImageSurfaceTexture::Destroy() {
+  surface_texture_ = NULL;
+  texture_id_ = 0;
+}
+
+gfx::Size GLImageSurfaceTexture::GetSize() { return size_; }
+
+bool GLImageSurfaceTexture::BindTexImage(unsigned target) {
+  TRACE_EVENT0("gpu", "GLImageSurfaceTexture::BindTexImage");
+
+  if (target != GL_TEXTURE_EXTERNAL_OES) {
+    LOG(ERROR)
+        << "Surface texture can only be bound to TEXTURE_EXTERNAL_OES target";
+    return false;
+  }
+
+  int texture_id;
+  glGetIntegerv(GL_TEXTURE_BINDING_EXTERNAL_OES, &texture_id);
+  DCHECK(texture_id);
+
+  if (texture_id_ && texture_id_ != texture_id) {
+    LOG(ERROR) << "Surface texture can only be bound to one texture ID";
+    return false;
+  }
+
+  DCHECK(surface_texture_);
+  if (texture_id != texture_id_) {
+    DetachFromGLContext(surface_texture_.get());
+    surface_texture_->AttachToGLContext();
+    texture_id_ = texture_id;
+  }
+
+  surface_texture_->UpdateTexImage();

[no sievers, 2014/03/18 20:58:13]

So whenever we updated the contents from the client side (releaseTexImage, lock,
unlockAndPost), we'd end up calling glBindTexImage2D again, right?

Maybe nothing to worry about now, but note that unfortunately SurfaceTexture
does not support the idea of GL share groups. It checks and remembers the
context handle whenever you call a SurfaceTexture API that needs a context (such
as updateTexImage()) and bails out if you ever call such again with a different
context current.

[reveman, 2014/03/24 18:35:07]

Yes, no guarantee that updated contents will be used unless BindTexImage2D is
called. 
Ok, good to know.

+  return true;
+}
+
+}  // namespace gfx