Invalidate m_image after GPU-GPU texture copy

third_party/WebKit/Source/platform/graphics/StaticBitmapImage.cpp

 // 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 "platform/graphics/StaticBitmapImage.h"
 
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/ImageObserver.h"
 #include "public/platform/Platform.h"
@@ skipping 95 matching lines @@
 {
     GLuint textureId = textureIdForWebGL(provider);
     gpu::gles2::GLES2Interface* gl = provider->contextGL();
     if (!gl)
         return;
     gl->CopyTextureCHROMIUM(textureId, destinationTexture, internalFormat, destType, flipY, false, false);
     const GLuint64 fenceSync = gl->InsertFenceSyncCHROMIUM();
     gl->Flush();
     GLbyte syncToken[24];
     gl->GenSyncTokenCHROMIUM(fenceSync, syncToken);
+    m_image = nullptr;

[Justin Novosad, 2016/07/20 15:07:52]

I think a better place for this would be at the end of switchStorageToMailbox

[xidachen, 2016/07/20 15:28:24]

I don't think that would work. I tried, and what happened is this:
at the end of switchStorageToMailbox, we set m_image = nullptr;
After that, we need to call gl->CopyTextureCHROMIUM(), that fails with error: GL
ERROR :GL_INVALID_VALUE : glCopyTextureCHROMIUM: unknown texture id

I believe that in order to have a valid texture id, the m_image has to be alive.
Does that make sense?

[Justin Novosad, 2016/07/20 15:51:59]

Sorry. Here you need to call switchStorageToMailbox, and at the end of
switchStorageToMailbox is where you'd reset m_image to null.  The fix you have
now loses the texture forever.

Also, for clarity, I think textureIdForWebGL should be renamed
switchStorageToSkImageForWebGL

[xidachen, 2016/07/20 16:47:27]

Right, that makes perfect sense, changed in the new PS.

 }
 
 bool StaticBitmapImage::switchStorageToMailbox(WebGraphicsContext3DProvider* provider)
 {
     m_mailbox.textureSize = WebSize(m_image->width(), m_image->height());
     GrContext* grContext = provider->grContext();
     if (!grContext)
         return false;
     grContext->flush();
     m_mailbox.textureTarget = GL_TEXTURE_2D;
@@ skipping 49 matching lines @@
     // Has mailbox, consume mailbox, prepare a new mailbox if contextProvider is not null (3D).
     DCHECK(isMainThread());
     // TODO(xidachen): make this work on a worker thread.
     std::unique_ptr<WebGraphicsContext3DProvider> sharedProvider = wrapUnique(Platform::current()->createSharedOffscreenGraphicsContext3DProvider());
     if (!switchStorageToSkImage(sharedProvider.get()))
         return nullptr;
     return m_image;
 }
 
 } // namespace blink