Specialize base::IsWeakReceiver for Blink weak pointers to support base::Bind (1/5)

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 903 matching lines @@
     m_maxViewportDims[0] = m_maxViewportDims[1] = 0;
     contextProvider->contextGL()->GetIntegerv(GL_MAX_VIEWPORT_DIMS, m_maxViewportDims);
 
     RefPtr<DrawingBuffer> buffer = createDrawingBuffer(std::move(contextProvider));
     if (!buffer) {
         m_contextLostMode = SyntheticLostContext;
         return;
     }
 
     m_drawingBuffer = buffer.release();
-    m_drawingBuffer->addNewMailboxCallback(WTF::bind(&WebGLRenderingContextBase::notifyCanvasContextChanged, createWeakThisPointer()));
+    m_drawingBuffer->addNewMailboxCallback(WTF::bind(&WebGLRenderingContextBase::notifyCanvasContextChanged, wrapWeakPersistent(this)));
     drawingBuffer()->bind(GL_FRAMEBUFFER);
     setupFlags();
 
 #define ADD_VALUES_TO_SET(set, values) \
     for (size_t i = 0; i < WTF_ARRAY_LENGTH(values); ++i) {   \
         set.insert(values[i]);                         \
     }
 
     ADD_VALUES_TO_SET(m_supportedInternalFormats, kSupportedInternalFormatsES2);
     ADD_VALUES_TO_SET(m_supportedInternalFormatsCopyTexImage, kSupportedInternalFormatsES2);
@@ skipping 99 matching lines @@
     m_boundVertexArrayObject = m_defaultVertexArrayObject;
 
     m_vertexAttribType.resize(m_maxVertexAttribs);
 
     contextGL()->Viewport(0, 0, drawingBufferWidth(), drawingBufferHeight());
     contextGL()->Scissor(0, 0, drawingBufferWidth(), drawingBufferHeight());
 
     drawingBuffer()->contextProvider()->setLostContextCallback(
         WebClosure(bind(
             &WebGLRenderingContextBase::forceLostContext,
-            createWeakThisPointer(),
+            wrapWeakPersistent(this),
             WebGLRenderingContextBase::RealLostContext,
             WebGLRenderingContextBase::Auto)));
     drawingBuffer()->contextProvider()->setErrorMessageCallback(
         WebFunction<void(const char*, int32_t)>(bind(
             &WebGLRenderingContextBase::onErrorMessage,
-            createWeakThisPointer())));
+            wrapWeakPersistent(this))));
 
     // If WebGL 2, the PRIMITIVE_RESTART_FIXED_INDEX should be always enabled.
     // See the section <Primitive Restart is Always Enabled> in WebGL 2 spec:
     // https://www.khronos.org/registry/webgl/specs/latest/2.0/#4.1.4
     if (isWebGL2OrHigher())
         contextGL()->Enable(GL_PRIMITIVE_RESTART_FIXED_INDEX);
 
     // This ensures that the context has a valid "lastFlushID" and won't be mistakenly identified as the "least recently used" context.
     contextGL()->Flush();
 
@@ skipping 90 matching lines @@
 
 void WebGLRenderingContextBase::destroyContext()
 {
     if (!drawingBuffer())
         return;
 
     m_extensionsUtil.reset();
 
     drawingBuffer()->contextProvider()->setLostContextCallback(WebClosure());
     drawingBuffer()->contextProvider()->setErrorMessageCallback(WebFunction<void(const char*, int32_t)>());
+    drawingBuffer()->addNewMailboxCallback(nullptr);

[sof, 2016/06/24 05:24:08]

It makes sense, but why is this needed now?

[tzik, 2016/06/24 05:57:06]

The error caught a Persistent leak after the termination GC.
That's due to DrawingBuffer holds a WeakPersintent of WebGLRendingContextBase
through the WTF::Function, and probably lives after the heap shutdown.
I don't know why the test didn't catch CrossThreadWeakPersistent...

[sof, 2016/06/24 06:45:32]

CT(W)Ps are exempt from checking for leaks when running termination GCs.

But why would the main thread be running a termination GC?

[tzik, 2016/06/24 07:04:58]

Makes sense.
The instance seems to be created on other thread than main according to line
578.

 
     ASSERT(drawingBuffer());
     m_drawingBuffer->beginDestruction();
     m_drawingBuffer.clear();
 }
 
 void WebGLRenderingContextBase::markContextChanged(ContentChangeType changeType)
 {
     if (m_framebufferBinding || isContextLost())
         return;
@@ skipping 4931 matching lines @@
         if (m_contextLostMode == RealLostContext) {
             m_restoreTimer.startOneShot(secondsBetweenRestoreAttempts, BLINK_FROM_HERE);
         } else {
             // This likely shouldn't happen but is the best way to report it to the WebGL app.
             synthesizeGLError(GL_INVALID_OPERATION, "", "error restoring context");
         }
         return;
     }
 
     m_drawingBuffer = buffer.release();
-    m_drawingBuffer->addNewMailboxCallback(WTF::bind(&WebGLRenderingContextBase::notifyCanvasContextChanged, createWeakThisPointer()));
+    m_drawingBuffer->addNewMailboxCallback(WTF::bind(&WebGLRenderingContextBase::notifyCanvasContextChanged, wrapWeakPersistent(this)));
 
     drawingBuffer()->bind(GL_FRAMEBUFFER);
     m_lostContextErrors.clear();
     m_contextLostMode = NotLostContext;
     m_autoRecoveryMethod = Manual;
     m_restoreAllowed = false;
     removeFromEvictedList(this);
 
     setupFlags();
     initializeNewContext();
@@ skipping 301 matching lines @@
         contextGL()->PixelStorei(GL_UNPACK_ALIGNMENT, 1);
 }
 
 void WebGLRenderingContextBase::restoreUnpackParameters()
 {
     if (m_unpackAlignment != 1)
         contextGL()->PixelStorei(GL_UNPACK_ALIGNMENT, m_unpackAlignment);
 }
 
 } // namespace blink