This is initial API support required for enabling SurfaceTexture backed zero-copy for Android

ui/gl/android/surface_texture.h

 // Copyright 2013 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.
 
 #ifndef UI_GL_ANDROID_SURFACE_TEXTURE_H_
 #define UI_GL_ANDROID_SURFACE_TEXTURE_H_
 
 #include <jni.h>
 
 #include "base/android/scoped_java_ref.h"
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "ui/gl/gl_export.h"
 
 struct ANativeWindow;
 
 namespace gfx {
 
 // This class serves as a bridge for native code to call java functions inside
 // android SurfaceTexture class.
 class GL_EXPORT SurfaceTexture
     : public base::RefCountedThreadSafe<SurfaceTexture>{
  public:
-  explicit SurfaceTexture(int texture_id);
+  static scoped_refptr<SurfaceTexture> Create(int texture_id);
+
+  static scoped_refptr<SurfaceTexture> CreateSingleBuffered(int texture_id);
 
   // Set the listener callback, which will be invoked on the same thread that
   // is being called from here for registration.
   // Note: Since callbacks come in from Java objects that might outlive objects
   // being referenced from the callback, the only robust way here is to create
   // the callback from a weak pointer to your object.
   void SetFrameAvailableCallback(const base::Closure& callback);
 
   // Update the texture image to the most recent frame from the image stream.
   void UpdateTexImage();
 
+  // Release the texture content. This is needed, and supported only in single
+  // buffered mode to allow the image content producer to take ownership
+  // of the image buffer.

[bulach, 2014/03/11 16:13:17]

nit: I'd be even more explicit:
this is *only* supported on SurfaceTexture instantiated via
|CreateSingleBuffered(...)|.

+  void ReleaseTexImage();
+
   // Retrieve the 4x4 texture coordinate transform matrix associated with the
   // texture image set by the most recent call to updateTexImage.
   void GetTransformMatrix(float mtx[16]);
 
   // Set the default size of the image buffers.
   void SetDefaultBufferSize(int width, int height);
 
   // Attach the SurfaceTexture to the texture currently bound to
   // GL_TEXTURE_EXTERNAL_OES.
   void AttachToGLContext();
 
   // Detaches the SurfaceTexture from the context that owns its current GL
   // texture. Must be called with that context current on the calling thread.
   void DetachFromGLContext();
 
   // Creates a native render surface for this surface texture.
   // The caller must release the underlying reference when done with the handle
   // by calling ANativeWindow_release().
   ANativeWindow* CreateSurface();
 
   const base::android::JavaRef<jobject>& j_surface_texture() const {
     return j_surface_texture_;
   }
 
+  static bool IsSingleBufferModeSupported();

[bulach, 2014/03/11 16:13:17]

nit: hmm... do we need a non-static method too?

I'm thinking about the following pattern:
scoped_refptr<SurfaceTexture> s = SurfaceTexture::Create(0);
if (SurfaceTexture::IsSingleBufferModeSupported()) {
  s->ReleaseTexImage();
}


should we document that this should only be used to guard the
CreateSingleBuffered() call?

+
   static bool RegisterSurfaceTexture(JNIEnv* env);
 
+ protected:
+  explicit SurfaceTexture(
+      const base::android::ScopedJavaLocalRef<jobject>& j_surface_texture);
+
  private:
   friend class base::RefCountedThreadSafe<SurfaceTexture>;
   ~SurfaceTexture();
 
   // Java SurfaceTexture instance.
   base::android::ScopedJavaGlobalRef<jobject> j_surface_texture_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceTexture);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_ANDROID_SURFACE_TEXTURE_H_